Pension and Other Postretirement Benefits - Contributions for Pension and Other Postretirement Benefits (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
U.S. Defined Benefit Pension Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	$ 0	$ 5,000
U.K. Defined Benefit Pension Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	1,405	1,308
Other Postretirement Benefits Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	438	436
U.K. Defined Contribution Pension Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	$ 300	$ 227