Description of Business and Summary of Significant Accounting Policies - Condensed Consolidated Balance Sheets (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Receivables $ 314,959 $ 269,144    
Total current assets 408,388 320,616    
Total Assets 843,811 636,389    
Other accrued liabilities 40,657 37,409    
Total current liabilities 288,411 245,079    
Deferred tax liability 39,386 49,407    
Total non-current liabilities 250,462 132,445    
Total Liabilities 538,873 377,524    
Retained earnings 222,026 185,075    
Total shareholders' equity 304,938 258,865 $ 220,324 $ 182,606
Total Liabilities and Shareholders' Equity $ 843,811 636,389    
As Previously Reported        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Receivables   269,239    
Total current assets   320,711    
Total Assets   636,484    
Other accrued liabilities   34,587    
Total current liabilities   242,257    
Deferred tax liability   49,808    
Total non-current liabilities   132,846    
Total Liabilities   375,103    
Retained earnings   187,591    
Total shareholders' equity   261,381 221,300 183,372
Total Liabilities and Shareholders' Equity   636,484    
Correction        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Receivables   (95)    
Total current assets   (95)    
Total Assets   (95)    
Other accrued liabilities   2,822    
Total current liabilities   2,822    
Deferred tax liability   (401)    
Total non-current liabilities   (401)    
Total Liabilities   2,421    
Retained earnings   (2,516)    
Total shareholders' equity   (2,516) $ (976) $ (766)
Total Liabilities and Shareholders' Equity   $ (95)