Segment Information - Summarized Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ 1,792,430	$ 1,872,340	$ 3,506,167	$ 3,733,726
Operating income (loss)	35,469	68,851	72,763	153,001
Depreciation	42,759	41,030	83,929	80,428
Electric Power Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Revenues	1,159,087	1,222,324	2,346,089	2,462,616
Operating income (loss)	75,934	88,027	163,258	197,019
Depreciation	22,937	22,072	45,882	42,989
Oil and Gas Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Revenues	633,343	650,016	1,160,078	1,271,110
Operating income (loss)	11,899	35,981	17,740	60,128
Depreciation	17,254	16,783	33,055	33,252
Corporate and Non-Allocated Costs [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	(52,364)	(55,157)	(108,235)	(104,146)
Depreciation	$ 2,568	$ 2,175	$ 4,992	$ 4,187