Pension and Other Postretirement Benefits - Net Periodic Pension and Other Postretirement Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
U.S. Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 921	$ 1,106	$ 2,762	$ 3,318
Interest cost	2,190	2,016	6,571	6,052
Expected return on plan assets	(2,686)	(2,342)	(8,060)	(7,026)
Amortization of prior service cost	213	160	640	480
Amortization of actuarial loss	1,046	1,788	3,138	5,360
Net benefit cost	1,684	2,728	5,051	8,184
U.K. Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	679	656	2,048	1,891
Expected return on plan assets	(795)	(651)	(2,399)	(1,842)
Amortization of actuarial loss	151	202	455	509
Net benefit cost	35	207	104	558
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	90	235	415	707
Interest cost	138	232	550	695
Amortization of prior service cost	(168)	21	(274)	64
Amortization of actuarial loss	47	61	57	181
Net benefit cost	$ 107	$ 549	$ 748	$ 1,647