Revenue Recognition (Tables)
   | 
9 Months Ended | 
Sep. 30, 2018  | 
| Revenue From Contract With Customer [Abstract] | 
 
 | 
| Revenue by customer and timing recognition | 
 
		
			Revenue by customer type was as follows:
		 
		
			 
		 
		
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Three Months Ended September 30, 2018 
				 | 
				
					 
						Work Truck Attachments 
				 | 
				
					 
						Work Truck Solutions 
				 | 
				
					 
						Corporate and Eliminations 
				 | 
				
					 
						Total Revenue 
				 | 
			 
			
				| 
					 
						Independent dealer 
				 | 
				
					 
						$ 80,964 
				 | 
				
					 
						$ 18,732 
				 | 
				
					 
						$ - 
				 | 
				
					 
						$ 99,696 
				 | 
			 
			
				| 
					 
						Government  
				 | 
				
					 
						 12,568 
				 | 
				
					 
						  - 
				 | 
				
					 
						  - 
				 | 
				
					 
						 12,568 
				 | 
			 
			
				| 
					 
						Fleet 
				 | 
				
					 
						  - 
				 | 
				
					 
						 13,955 
				 | 
				
					 
						  - 
				 | 
				
					 
						 13,955 
				 | 
			 
			
				| 
					 
						Other 
				 | 
				
					 
						  - 
				 | 
				
					 
						 2,017 
				 | 
				
					 
						 (3,404) 
				 | 
				
					 
						 (1,387) 
				 | 
			 
			
				| 
					 
						Total revenue 
				 | 
				
					 
						$ 93,532 
				 | 
				
					 
						$ 34,704 
				 | 
				
					 
						$ (3,404) 
				 | 
				
					 
						$ 124,832 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Nine Months Ended September 30, 2018 
				 | 
				
					 
						Work Truck Attachments 
				 | 
				
					 
						Work Truck Solutions 
				 | 
				
					 
						Corporate and Eliminations 
				 | 
				
					 
						Total Revenue 
				 | 
			 
			
				| 
					 
						Independent dealer 
				 | 
				
					 
						$ 232,934 
				 | 
				
					 
						$ 58,524 
				 | 
				
					 
						$ - 
				 | 
				
					 
						$ 291,458 
				 | 
			 
			
				| 
					 
						Government  
				 | 
				
					 
						 35,351 
				 | 
				
					 
						  - 
				 | 
				
					 
						  - 
				 | 
				
					 
						 35,351 
				 | 
			 
			
				| 
					 
						Fleet 
				 | 
				
					 
						  - 
				 | 
				
					 
						 43,501 
				 | 
				
					 
						  - 
				 | 
				
					 
						 43,501 
				 | 
			 
			
				| 
					 
						Other 
				 | 
				
					 
						  - 
				 | 
				
					 
						 8,538 
				 | 
				
					 
						 (6,606) 
				 | 
				
					 
						 1,932 
				 | 
			 
			
				| 
					 
						Total revenue 
				 | 
				
					 
						$ 268,285 
				 | 
				
					 
						$ 110,563 
				 | 
				
					 
						$ (6,606) 
				 | 
				
					 
						$ 372,242 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
		  
		
			Revenue by timing of revenue recognition was as follows:
		 
		
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Three Months Ended September 30, 2018 
				 | 
				
					 
						Work Truck Attachments 
				 | 
				
					 
						Work Truck Solutions 
				 | 
				
					 
						Corporate and Eliminations 
				 | 
				
					 
						Total Revenue 
				 | 
			 
			
				| 
					 
						Point in time 
				 | 
				
					 
						$ 93,532 
				 | 
				
					 
						$ 13,601 
				 | 
				
					 
						$ (3,404) 
				 | 
				
					 
						$ 103,729 
				 | 
			 
			
				| 
					 
						Over time 
				 | 
				
					 
						  - 
				 | 
				
					 
						 21,103 
				 | 
				
					 
						  - 
				 | 
				
					 
						 21,103 
				 | 
			 
			
				| 
					 
						Total revenue 
				 | 
				
					 
						$ 93,532 
				 | 
				
					 
						$ 34,704 
				 | 
				
					 
						$ (3,404) 
				 | 
				
					 
						$ 124,832 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Nine Months Ended September 30, 2018 
				 | 
				
					 
						Work Truck Attachments 
				 | 
				
					 
						Work Truck Solutions 
				 | 
				
					 
						Corporate and Eliminations 
				 | 
				
					 
						Total Revenue 
				 | 
			 
			
				| 
					 
						Point in time 
				 | 
				
					 
						$ 268,285 
				 | 
				
					 
						$ 42,501 
				 | 
				
					 
						$ (6,606) 
				 | 
				
					 
						$ 304,180 
				 | 
			 
			
				| 
					 
						Over time 
				 | 
				
					 
						  - 
				 | 
				
					 
						 68,062 
				 | 
				
					 
						  - 
				 | 
				
					 
						 68,062 
				 | 
			 
			
				| 
					 
						Total revenue 
				 | 
				
					 
						$ 268,285 
				 | 
				
					 
						$ 110,563 
				 | 
				
					 
						$ (6,606) 
				 | 
				
					 
						$ 372,242 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
		  
		
			 
		 
   
 | 
| Contract Balances | 
 
		
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Three Months Ended September 30, 2018 
				 | 
				
					 
						  
				 | 
				
					 
						Balance at Beginning of Period 
				 | 
				
					 
						  
				 | 
				
					 
						Additions 
				 | 
				
					 
						  
				 | 
				
					 
						Deductions 
				 | 
				
					 
						  
				 | 
				
					 
						Balance at End of Period 
				 | 
			 
			
				| 
					 
						Contract liabilities 
				 | 
				
					 
						$ 
				 | 
				
					 
						 3,316 
				 | 
				
					 
						$ 
				 | 
				
					 
						 2,434 
				 | 
				
					 
						$ 
				 | 
				
					 
						 (3,544) 
				 | 
				
					 
						$ 
				 | 
				
					 
						 2,206 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Nine Months Ended September 30, 2018 
				 | 
				
					 
						  
				 | 
				
					 
						Balance at Beginning of Period 
				 | 
				
					 
						  
				 | 
				
					 
						Additions 
				 | 
				
					 
						  
				 | 
				
					 
						Deductions 
				 | 
				
					 
						  
				 | 
				
					 
						Balance at End of Period 
				 | 
			 
			
				| 
					 
						Contract liabilities 
				 | 
				
					 
						$ 
				 | 
				
					 
						 2,048 
				 | 
				
					 
						$ 
				 | 
				
					 
						 8,605 
				 | 
				
					 
						$ 
				 | 
				
					 
						 (8,447) 
				 | 
				
					 
						$ 
				 | 
				
					 
						 2,206 
				 | 
			 
		  
		
			 
		 
   
 | 
| Impact of New Revenue Guidance on Financial Statement Line Items | 
 
		
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						Three Months Ended September 30, 2018 
				 | 
				
					 
						  
				 | 
				
					 
						Nine Months Ended September 30, 2018 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						As Reported 
				 | 
				
					 
						Balances without adoption of Topic 606 
				 | 
				
					 
						Effect of Change Higher/(Lower) 
				 | 
				
					 
						  
				 | 
				
					 
						As Reported 
				 | 
				
					 
						Balances without adoption of Topic 606 
				 | 
				
					 
						Effect of Change Higher/(Lower) 
				 | 
			 
			
				| 
					 
						Net sales 
				 | 
				
					 
						$ 124,832 
				 | 
				
					 
						$ 124,816 
				 | 
				
					 
						$ 16 
				 | 
				
					 
						  
				 | 
				
					 
						$ 372,242 
				 | 
				
					 
						$ 371,969 
				 | 
				
					 
						$ 273 
				 | 
			 
			
				| 
					 
						Cost of sales 
				 | 
				
					 
						 89,912 
				 | 
				
					 
						 89,910 
				 | 
				
					 
						  2 
				 | 
				
					 
						  
				 | 
				
					 
						 261,446 
				 | 
				
					 
						 261,276 
				 | 
				
					 
						 170 
				 | 
			 
			
				| 
					 
						Gross profit 
				 | 
				
					 
						 34,920 
				 | 
				
					 
						 34,906 
				 | 
				
					 
						 14 
				 | 
				
					 
						  
				 | 
				
					 
						 110,796 
				 | 
				
					 
						 110,693 
				 | 
				
					 
						 103 
				 | 
			 
			
				| 
					 
						Income from operations 
				 | 
				
					 
						 15,460 
				 | 
				
					 
						 15,446 
				 | 
				
					 
						 14 
				 | 
				
					 
						  
				 | 
				
					 
						 48,910 
				 | 
				
					 
						 48,807 
				 | 
				
					 
						 103 
				 | 
			 
			
				| 
					 
						Income tax expense 
				 | 
				
					 
						 1,148 
				 | 
				
					 
						 1,144 
				 | 
				
					 
						  4 
				 | 
				
					 
						  
				 | 
				
					 
						 6,802 
				 | 
				
					 
						 6,774 
				 | 
				
					 
						 28 
				 | 
			 
			
				| 
					 
						Net income 
				 | 
				
					 
						$ 9,921 
				 | 
				
					 
						$ 9,911 
				 | 
				
					 
						$ 10 
				 | 
				
					 
						  
				 | 
				
					 
						$ 29,209 
				 | 
				
					 
						$ 29,134 
				 | 
				
					 
						$ 75 
				 | 
			 
			
				| 
					 
						Earnings per common share: 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Basic 
				 | 
				
					 
						$ 0.43 
				 | 
				
					 
						$ - 
				 | 
				
					 
						$ 0.43 
				 | 
				
					 
						  
				 | 
				
					 
						$ 1.27 
				 | 
				
					 
						$ - 
				 | 
				
					 
						$ 1.27 
				 | 
			 
			
				| 
					 
						Diluted 
				 | 
				
					 
						$ 0.43 
				 | 
				
					 
						$ - 
				 | 
				
					 
						$ 0.43 
				 | 
				
					 
						  
				 | 
				
					 
						$ 1.26 
				 | 
				
					 
						$ - 
				 | 
				
					 
						$ 1.26 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
		  
		
			 
		 
		
			 
		 
		
			 
		 
		
			 
		 
		
			 
		 
		
			 
		 
		
			In accordance with Topic 606, the disclosure of the impact of adoption to the condensed consolidated balance sheet was as follows:
		 
		
			 
		 
		
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						As of September 30, 2018 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						As Reported 
				 | 
				
					 
						Balances without adoption of Topic 606 
				 | 
				
					 
						Effect of Change Higher/(Lower) 
				 | 
			 
			
				| 
					 
						Assets: 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Accounts Receivable 
				 | 
				
					 
						$ 128,164 
				 | 
				
					 
						$ 126,052 
				 | 
				
					 
						$ 2,112 
				 | 
			 
			
				| 
					 
						Inventory 
				 | 
				
					 
						 89,444 
				 | 
				
					 
						 91,148 
				 | 
				
					 
						 (1,704) 
				 | 
			 
			
				| 
					 
						Liabilities: 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Deferred tax liability 
				 | 
				
					 
						 46,447 
				 | 
				
					 
						 46,341 
				 | 
				
					 
						 106 
				 | 
			 
			
				| 
					 
						Shareholder's Equity: 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Retained Earnings 
				 | 
				
					 
						 127,032 
				 | 
				
					 
						 126,654 
				 | 
				
					 
						 378 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
		  
		
			 
		 
   
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