Acquisitions and Dispositions - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			0 Months Ended	3 Months Ended	6 Months Ended	0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Nuclear Projects [Member]	Jun. 30, 2013 Nuclear Projects [Member]	Jun. 30, 2014 Nuclear Projects [Member]	Jun. 30, 2013 Nuclear Projects [Member]	Jun. 30, 2014 Acquisition-related Costs [Member]	Jun. 30, 2013 Acquisition-related Costs [Member]	Jun. 30, 2014 Acquisition-related Costs [Member]	Jun. 30, 2013 Acquisition-related Costs [Member]	Jul. 11, 2014 Subsequent Event [Member] Nuclear Projects [Member]	Jun. 20, 2014 MEGTEC Holdings Inc [Member]	Jun. 30, 2014 MEGTEC Holdings Inc [Member]	Jun. 30, 2014 MEGTEC Holdings Inc [Member]	May 21, 2014 Ebensberg Power Company [Member]
Significant Acquisitions and Disposals [Line Items]
Payments to acquire business			$ 127,098,000											$ 142,200,000
Revenues	686,006,000	886,136,000	1,348,023,000	1,691,559,000											3,600,000	3,600,000
Net Income	26,437,000	72,870,000	71,481,000	120,044,000											200,000	200,000
Amortization expense related to identifiable intangible assets									800,000	2,800,000	1,300,000	5,600,000
Elimination of historical interest expense									600,000	400,000	900,000	900,000
Interest expense associated with incremental borrowings									600,000	600,000	1,200,000	1,300,000
Elimination of acquisition related costs									13,500,000		13,500,000
Payment to acquire business																	1,300,000
Business acquisition, cash acquired															14,232,000	14,232,000	16,400,000
Business acquisition, plant and equipment acquired															5,090,000	5,090,000	16,100,000
Income (loss) before provision for income taxes					0	(500,000)	(100,000)	(1,000,000)
Accounts receivable					37,500,000		37,500,000
Contracts in progress					8,200,000		8,200,000
Lien filed against property													$ 37,400,000