Pension and Other Postretirement Benefits - Contributions for Pension and Other Postretirement Benefits (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Other Postretirement Benefit Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	$ 852	$ 1,092
Foreign Defined Benefits Pension Plans [Member] | Defined Benefit Pension Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	1,323	1,260
Foreign Defined Benefits Pension Plans [Member] | Defined Benefit Pension Plan [Member] | U.K. [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	223	182
U.S. Defined Benefit Pension Plans [Member] | Defined Benefit Pension Plan [Member] | U.S. [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Contributions	$ 1,788	$ 1,792