Basis of Presentation and Significant Accounting Policies - Changes in Carrying Amount of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Power Generation [Member]	Jun. 30, 2014 Nuclear Operations [Member]	Dec. 31, 2013 Nuclear Operations [Member]	Jun. 30, 2014 Technical Services [Member]	Dec. 31, 2013 Technical Services [Member]	Jun. 30, 2014 Nuclear Energy [Member]	Dec. 31, 2013 Nuclear Energy [Member]
Goodwill [Line Items]
Beginning balance	$ 281,708	$ 104,630	$ 118,103	$ 118,103	$ 45,000	$ 45,000	$ 13,975	$ 13,975
Acquisition of MEGTEC (Note 2)	115,314	115,314
Foreign currency translation adjustments and other	(193)	(193)
Balance at June 30, 2014	$ 396,829	$ 219,751	$ 118,103	$ 118,103	$ 45,000	$ 45,000	$ 13,975	$ 13,975