Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Revenue Recognition (Detail)

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Summary of Significant Accounting Policies - Revenue Recognition (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Jan. 01, 2018
Dec. 31, 2017
Revenue Recognition [Line Items]            
Revenue recognized related to amounts in contract liabilities outstanding at the beginning of period $ 79,000   $ 343,000      
Revenue, remaining performance obligation $ 5,580,000   $ 5,580,000      
Revenue, remaining performance obligation expected to be recognized within twelve months 79.80%   79.80%      
Change orders and/or claims $ 110,600   $ 110,600     $ 144,000
Revenue, related to performance obligation satisfied in previous periods 15,800   47,400      
Change in contract estimates, impact on operating results, gain (loss) $ 800 $ 28,800 $ 14,200 $ 31,000    
Percent aggregate change in contract estimates impact on gross margin 0.20% 9.50% 2.20% 5.50%    
Accounts payable and accrued expenses $ 1,178,983   $ 1,178,983     1,057,460
EPC Electric Transmission Project            
Revenue Recognition [Line Items]            
Change in contract estimates, impact on operating results, gain (loss) 16,600   26,300      
Natural Gas Transmission Project            
Revenue Recognition [Line Items]            
Change in contract estimates, impact on operating results, gain (loss)   $ 24,600        
Retained Earnings | Accounting Standards Update 2014-09            
Revenue Recognition [Line Items]            
Cumulative effect adjustment         $ (1,800)  
Unearned Revenue            
Revenue Recognition [Line Items]            
Accounts payable and accrued expenses $ 11,400   $ 11,400     $ 16,000