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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Dec. 31, 2012
Jun. 30, 2013
Jun. 30, 2012
Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]                
Cash and cash equivalents $ 309,153,000 $ 128,209,000 $ 309,153,000 $ 128,209,000 $ 394,701,000 $ 363,113,000 $ 172,868,000 $ 315,349,000
Cash equivalents 130,100,000   130,100,000   92,500,000      
Cash and cash equivalents held in domestic bank accounts 125,200,000   125,200,000   254,100,000      
Cash and cash equivalents held in foreign bank accounts 184,000,000   184,000,000   140,600,000      
Number of days after accounts receivable are treated as delinquent 30 days   30 days   30 days      
Number of days related to outstanding accounts receivable for analysis of the allowance for doubtful accounts     At least 90 days          
Total allowances for doubtful accounts 5,256,000   5,256,000   5,447,000      
Current retainage balances 222,900,000   222,900,000   180,600,000      
Non-current retainage balances 42,300,000   42,300,000   22,500,000      
Unbilled receivables 193,100,000   193,100,000   127,500,000      
Decrease in fair value of reporting units considered, for impairment calculation         10.00%      
Payment to acquire equity method investment 1,707,000   11,177,000 53,750,000        
Percent change in contract estimates impact on gross margin is not more than this percentage     5.00%          
Change orders and/or claims 241,300,000   241,300,000   205,000,000      
Revenue associated with change order 1,645,132,000 1,532,001,000 4,705,219,000 4,246,927,000        
Fiber Optic Licensing Terms, Minimum in years 5 years 5 years 5 years 5 years 5 years      
Fiber Optic Licensing Terms, Maximum in years 25 years 25 years 25 years 25 years 25 years      
Fiber optic deferred revenue 47,800,000   47,800,000   46,400,000      
Fiber optic non-current deferred revenue 38,800,000   38,800,000   37,700,000      
Total amount of unrecognized tax benefits relating to uncertain tax positions 50,600,000   50,600,000          
Amount of unrecognized tax benefits change from year-end relating to uncertain tax positions     600,000          
Amount expected to decrease due to settlements of audits or as a result of the expiration of certain statutes of limitations 10,800,000   10,800,000          
Decrease in unrecognized tax benefits     7,400,000          
Increase in unrecognized tax benefits     6,800,000          
Sunrise Powerlink Project [Member]
                
Summary Of Significant Accounting Policies [Line Items]                
Revenue associated with change order         165,000,000      
Howard Midstream Energy Partners, LLC. [Member]
                
Summary Of Significant Accounting Policies [Line Items]                
Equity Method Investment ownership 31.00%   31.00%          
Balance of equity ownership interest 99,600,000   99,600,000   90,500,000      
Payment to acquire equity method investment     $ 9,100,000          
Minimum [Member]
                
Summary Of Significant Accounting Policies [Line Items]                
Equity Method Investment ownership 20.00%   20.00%          
Maximum [Member]
                
Summary Of Significant Accounting Policies [Line Items]                
Equity Method Investment ownership 50.00%   50.00%