Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 366,619,000	$ 177,367,000	$ 394,701,000	$ 315,349,000
Cash equivalents	189,800,000		92,500,000
Cash and cash equivalents held in domestic bank accounts	254,700,000		254,100,000
Cash and cash equivalents held in foreign bank accounts	111,900,000		140,600,000
Number of days after accounts receivable are treated as delinquent	30 days		30 days
Number of days related to outstanding accounts receivable for analysis of the allowance for doubtful accounts	At least 90 days		At least 90 days
Total allowances for doubtful accounts	5,426,000		5,447,000
Current retainage balances	192,300,000		180,600,000
Non-current retainage balances	29,300,000		22,500,000
Unbilled receivables	144,300,000		127,500,000
Decrease in fair value of reporting units considered, for impairment calculation			10.00%
Payment to acquire equity method investment	8,545,000	4,906,000
Change orders and/or claims	222,400,000		205,000,000
Fiber Optic Licensing Terms, Minimum in years	5 years	5 years	5 years
Fiber Optic Licensing Terms, Maximum in years	25 years	25 years	25 years
Fiber optic deferred revenue	46,300,000		46,400,000
Fiber optic non-current deferred revenue	37,100,000		37,700,000
Total amount of unrecognized tax benefits relating to uncertain tax positions	53,500,000
Amount of unrecognized tax benefits change from year-end relating to uncertain tax positions	2,300,000
Amount expected to decrease due to settlements of audits or as a result of the expiration of certain statutes of limitations	11,500,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity Method Investment ownership	20.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity Method Investment ownership	50.00%
Howard Midstream Energy Partners, LLC. [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity Method Investment ownership	31.00%
Balance of equity ownership interest	99,000,000		90,500,000
Payment to acquire equity method investment	$ 8,500,000