Quarterly report pursuant to Section 13 or 15(d)

Revenue from Contracts with Customers - Summary of Impact of Adoption (Details)

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Revenue from Contracts with Customers - Summary of Impact of Adoption (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Jan. 01, 2018
Dec. 31, 2017
Income Statement [Abstract]        
Revenues $ 167,410 $ 134,610    
Cost of revenues 131,937 108,686    
Gross profit 35,473 25,924    
Operating expenses:        
Selling, general and administrative expenses 27,204 26,487    
Operating income 8,269 (563)    
Other expenses, net 3,544 1,826    
Income (loss) before benefit for income taxes 4,725 (2,389)    
Income tax benefit (2,779) (645)    
Net income (loss) 7,504 (1,744)    
Net (income) attributable to redeemable non-controlling interests (516) 1,100    
Net income (loss) attributable to common shareholders $ 6,988 $ (644)    
Basic income per share (in usd per share) $ 0.15 $ (0.01)    
Diluted income per share (in usd per share) $ 0.15 $ (0.01)    
Assets:        
Costs and estimated earnings in excess of billings $ 64,064   $ 95,658 $ 104,852
Prepaid expenses and other current assets 23,258   18,380 14,037
Deferred income taxes 3,570   1,003 0
Liabilities:        
Accrued expenses and other current liabilities 23,818   24,450 23,260
Deferred income taxes, net 0   0 584
Shareholders' Equity:        
Retained earnings 238,378   231,390 $ 235,844
Balances without adoption of Topic 606        
Income Statement [Abstract]        
Revenues 168,239      
Cost of revenues 134,161      
Gross profit 34,078      
Operating expenses:        
Selling, general and administrative expenses 27,204      
Operating income 6,874      
Other expenses, net 3,544      
Income (loss) before benefit for income taxes 3,330      
Income tax benefit (3,094)      
Net income (loss) 6,424      
Net (income) attributable to redeemable non-controlling interests (516)      
Net income (loss) attributable to common shareholders $ 5,908      
Basic income per share (in usd per share) $ 0.13      
Diluted income per share (in usd per share) $ 0.13      
Assets:        
Costs and estimated earnings in excess of billings $ 74,088   104,852  
Prepaid expenses and other current assets 16,523   14,037  
Deferred income taxes 2,298   0  
Liabilities:        
Accrued expenses and other current liabilities 22,490   23,260  
Deferred income taxes, net     584  
Shareholders' Equity:        
Retained earnings 241,723   235,844  
Accounting Standards Update 2014-09 | Effect of Change Higher/(Lower)        
Income Statement [Abstract]        
Revenues (829)      
Cost of revenues (2,224)      
Gross profit 1,395      
Operating expenses:        
Selling, general and administrative expenses 0      
Operating income 1,395      
Other expenses, net 0      
Income (loss) before benefit for income taxes 1,395      
Income tax benefit 315      
Net income (loss) 1,080      
Net (income) attributable to redeemable non-controlling interests 0      
Net income (loss) attributable to common shareholders $ 1,080      
Basic income per share (in usd per share) $ 0.02      
Diluted income per share (in usd per share) $ 0.02      
Assets:        
Costs and estimated earnings in excess of billings $ (10,024)   (9,194)  
Prepaid expenses and other current assets 6,735   4,343  
Deferred income taxes 1,272   1,003  
Liabilities:        
Accrued expenses and other current liabilities 1,328   1,190  
Deferred income taxes, net     (584)  
Shareholders' Equity:        
Retained earnings $ (3,345)   $ (4,454)