Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies (Revenue Recognition) - Additional Information (Detail)

v3.7.0.1
Summary of Significant Accounting Policies (Revenue Recognition) - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2016
Revenue Recognition [Line Items]      
Revenues $ 2,178,170,000 $ 1,713,737,000  
Project completion percentage 85.00%    
Change orders and/or claims $ 147,100,000   $ 137,800,000
Maximum [Member]      
Revenue Recognition [Line Items]      
Percent aggregate change in contract estimates impact on operating results is less than this percentage 5.00% 5.00%  
Natural Gas Transmission Project That Experienced Weather Delays [Member]      
Revenue Recognition [Line Items]      
Losses on Contracts $ 16,500,000    
Alaska Power Plant Construction Project [Member]      
Revenue Recognition [Line Items]      
Losses on Contracts   $ 21,300,000  
Revenue Recognized For Losses Member | Natural Gas Transmission Project That Experienced Weather Delays [Member]      
Revenue Recognition [Line Items]      
Revenues $ 0