Acquisition - Business Acquisition, Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands  | 
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019  | 
Jun. 30, 2018  | 
Jun. 30, 2019  | 
Jun. 30, 2018  | 
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| Business Combinations [Abstract] | ||||
| Revenue | $ 189,111 | $ 181,569 | $ 360,589 | $ 368,988 | 
| Net Income | $ 10,025 | $ 8,870 | $ 17,064 | $ 16,171 | 
| Basic earnings per share (in dollars per share) | $ 0.92 | $ 0.82 | $ 1.56 | $ 1.49 | 
| Diluted earnings per share (in dollars per share) | $ 0.91 | $ 0.81 | $ 1.55 | $ 1.48 | 
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- Definition The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- References No definition available. 
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