Pension and Other Postretirement Benefits - Summary of Changes in the Fair Value of the Level 3 Plan Assets for U.S. and Foreign Pension Plans (Detail) £ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 GBP (£)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
U.S. Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, Beginning balance	$ 139,376		$ 157,048
Contributions	376		324
Change in net unrealized (losses) gains	(160)		(9,880)
Other, primarily impact from changes in foreign currency exchange rates	0		0
Fair value of plan assets, Ending balance	188,722		139,376	$ 157,048
U.S. Pension Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, Beginning balance	37,177
Fair value of plan assets, Ending balance	33,830		37,177
U.S. Pension Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Hedge and Absolute Return Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, Beginning balance	4,967		8,592
Contributions	0		5,900
Withdrawals	(4,967)		(9,843)
Realized gains (losses)	0		2,334
Change in net unrealized (losses) gains	0		(2,016)
Other, primarily impact from changes in foreign currency exchange rates	0		0
Fair value of plan assets, Ending balance	0		4,967	8,592
U.S. Pension Benefits [Member] | Managed Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, Beginning balance	32,210		33,602
Contributions	0		0
Withdrawals	0		(2,424)
Realized gains (losses)	1,857		(19)
Change in net unrealized (losses) gains	(237)		1,051
Other, primarily impact from changes in foreign currency exchange rates	0		0
Fair value of plan assets, Ending balance	33,830		32,210	33,602
Foreign Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, Beginning balance	49,628	£ 33,528	50,533
Contributions	1,687		1,715	1,849
Change in net unrealized (losses) gains	8,869		(4,005)
Other, primarily impact from changes in foreign currency exchange rates	(8,930)		(2,572)
Fair value of plan assets, Ending balance	48,055	£ 38,955	49,628	50,533
Foreign Pension Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, Beginning balance	10,571		10,799
Contributions	0		0
Withdrawals	0		0
Realized gains (losses)	0		0
Change in net unrealized (losses) gains	(280)		320
Other, primarily impact from changes in foreign currency exchange rates	(1,698)		(548)
Fair value of plan assets, Ending balance	$ 8,593		$ 10,571	$ 10,799