Segments (Details) $ in Thousands  | 
3 Months Ended | 9 Months Ended | 12 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 
 Jul. 15, 2016  
segment 
 | 
 Dec. 31, 2017  
USD ($) 
 | 
 Sep. 30, 2017  
USD ($) 
 | 
 Jun. 30, 2017  
USD ($) 
 | 
 Mar. 31, 2017  
USD ($) 
 | 
 Dec. 31, 2016  
USD ($) 
 | 
 Sep. 30, 2016  
USD ($) 
 | 
 Jun. 30, 2016  
USD ($) 
 | 
 Mar. 31, 2016  
USD ($) 
 | 
 Sep. 30, 2016  
segment 
 | 
 Dec. 31, 2017  
USD ($)  
customer  
segment 
 | 
 Dec. 31, 2016  
USD ($) 
 | 
 Dec. 31, 2015  
USD ($) 
 | 
|
| Segment Reporting Information [Line Items] | |||||||||||||
| Number of operating segments | segment | 2 | 1 | 2 | ||||||||||
| Number of reportable segments | segment | 1 | 2 | |||||||||||
| Number of customers | customer | 0 | ||||||||||||
| Net sales | $ 137,969 | $ 125,339 | $ 139,371 | $ 72,248 | $ 130,143 | $ 123,573 | $ 113,763 | $ 48,789 | $ 474,927 | $ 416,268 | $ 400,408 | ||
| Gross profit (loss) | 44,811 | $ 36,055 | $ 45,033 | $ 17,187 | 41,678 | $ 36,644 | $ 41,521 | $ 14,131 | 143,086 | 133,974 | 132,863 | ||
| Selling, general and administrative expense | 61,594 | 54,260 | 48,150 | ||||||||||
| Income (loss) from operations | 70,091 | 69,118 | 77,351 | ||||||||||
| Depreciation expense | 7,183 | 6,146 | 4,919 | ||||||||||
| Assets | 685,176 | 666,173 | 685,176 | 666,173 | 497,012 | ||||||||
| Capital expenditures | 7,563 | 9,830 | 10,009 | ||||||||||
| Capital Expenditures including adjustments to accruals and payables | 8,380 | ||||||||||||
| Corporate & Eliminations | |||||||||||||
| Segment Reporting Information [Line Items] | |||||||||||||
| Net sales | (13,407) | (9,414) | 501 | ||||||||||
| Selling, general and administrative expense | 15,058 | 15,776 | 14,843 | ||||||||||
| Income (loss) from operations | (17,822) | (19,847) | (16,138) | ||||||||||
| Depreciation expense | 143 | 197 | 196 | ||||||||||
| Assets | 39,817 | 22,425 | 39,817 | 22,425 | 44,935 | ||||||||
| Capital expenditures | 29 | ||||||||||||
| Operating segment | Work Truck Attachments | |||||||||||||
| Segment Reporting Information [Line Items] | |||||||||||||
| Net sales | 350,564 | 360,638 | 399,907 | ||||||||||
| Selling, general and administrative expense | 31,398 | 31,181 | 33,307 | ||||||||||
| Income (loss) from operations | 78,088 | 85,888 | 93,489 | ||||||||||
| Depreciation expense | 5,533 | 5,377 | 4,723 | ||||||||||
| Assets | 425,148 | 439,937 | 425,148 | 439,937 | 452,077 | ||||||||
| Capital expenditures | 8,752 | $ 9,980 | |||||||||||
| Capital Expenditures including adjustments to accruals and payables | 6,408 | ||||||||||||
| Operating segment | Work Truck Solutions segment | |||||||||||||
| Segment Reporting Information [Line Items] | |||||||||||||
| Net sales | 137,770 | 65,044 | |||||||||||
| Selling, general and administrative expense | 15,138 | 7,303 | |||||||||||
| Income (loss) from operations | 9,825 | 3,077 | |||||||||||
| Depreciation expense | 1,507 | 572 | |||||||||||
| Assets | $ 220,211 | $ 203,811 | 220,211 | 203,811 | |||||||||
| Capital expenditures | $ 1,078 | ||||||||||||
| Capital Expenditures including adjustments to accruals and payables | $ 1,972 | ||||||||||||