Income Taxes - Uncertain tax positions (Details) - USD ($) $ in Thousands  | 
12 Months Ended | |||
|---|---|---|---|---|
Dec. 31, 2018  | 
Dec. 31, 2017  | 
Dec. 31, 2016  | 
Dec. 31, 2015  | 
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| A reconciliation of the beginning and ending liability for uncertain tax positions | ||||
| Balance at beginning of year | $ 3,531 | $ 2,361 | $ 490 | $ 464 | 
| Increase Resulting from Current Period Tax Positions | 97 | 73 | 26 | |
| Increases for tax position taken in prior years | 1,602 | 1,809 | ||
| Decreases due to settlements with taxing authorities | (8) | (11) | ||
| Decreases due to lapses in the statute of limitations | (521) | |||
| Balance at the end of year | 3,531 | 2,361 | $ 490 | |
| Unrecognized tax benefits that would affect the effective tax rate, if recognized | 1,706 | |||
| Accrued interest and penalties reported as income tax liability | $ 804 | $ 79 | ||
| U.S. corporate income tax rate | 35.00% | |||
| Net deferred tax liability | $ 22,452 | |||
| Forecast | ||||
| A reconciliation of the beginning and ending liability for uncertain tax positions | ||||
| U.S. corporate income tax rate | 21.00% | |||
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- Definition Amount of income tax expense for remeasurement of deferred tax asset from change in tax rate pursuant to Tax Cuts and Jobs Act of 2017. No definition available. 
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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available. 
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- Definition Amount of unrecognized tax benefits. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
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