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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
U.S. Pension Benefits Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	$ 1,106	$ 986	$ 3,318	$ 2,958
Interest cost	2,016	2,129	6,052	6,386
Expected return on plan assets	(2,342)	(2,389)	(7,026)	(7,167)
Amortization of prior service cost	160	167	480	501
Amortization of actuarial loss (gain)	1,788	1,522	5,360	4,565
Net benefit cost	2,728	2,415	8,184	7,243
U.K. Pension Benefits Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Interest cost	656	626	1,891	1,871
Expected return on plan assets	(651)	(525)	(1,842)	(1,569)
Amortization of actuarial loss (gain)	202	150	509	447
Net benefit cost	207	251	558	749
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	235	280	707	603
Interest cost	232	230	695	689
Amortization of prior service cost	21	21	64	64
Amortization of actuarial loss (gain)	61	(152)	181	54
Net benefit cost	$ 549	$ 379	$ 1,647	$ 1,410