Pension and Other Postretirement Benefits - Schedule of Changes in Plan Assets (Detail) In Thousands, unless otherwise specified	12 Months Ended		12 Months Ended							12 Months Ended
	Dec. 31, 2013 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2014 U.S. Pension Benefits [Member] USD ($)	Dec. 31, 2013 U.S. Pension Benefits [Member] USD ($)	Dec. 31, 2014 Foreign Pension Benefits [Member] USD ($)	Dec. 31, 2013 Foreign Pension Benefits [Member] USD ($)	Dec. 31, 2012 Foreign Pension Benefits [Member] USD ($)	Dec. 31, 2014 Foreign Pension Benefits [Member] GBP (£)	Dec. 31, 2013 Foreign Pension Benefits [Member] GBP (£)	Dec. 31, 2014 Other Postretirement Benefits [Member] USD ($)	Dec. 31, 2013 Other Postretirement Benefits [Member] USD ($)
Change in plan assets:
Fair value of plan assets, Beginning balance		$ 157,048	$ 164,085	$ 140,218	$ 48,536	$ 41,875		£ 32,437	£ 29,315	$ 0	$ 0
Actual return on plan assets			10,761	26,679	5,936	5,061				0	0
Foreign currency exchange rate changes			0	0	(3,144)	1,098				0	0
Corporate contributions	5,000		40	5,008	1,849	1,764	1,786			589	597
Participant contributions			0	0	0	0				386	423
Plan settlements			(9,304)	0	0	0				0	0
Gross benefits paid			(8,534)	(7,820)	(2,644)	(1,262)				(975)	(1,020)
Fair value of plan assets, Ending balance		$ 157,048	$ 157,048	$ 164,085	$ 50,533	$ 48,536	$ 41,875	£ 32,437	£ 29,315	$ 0	$ 0