Pensions - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Non-elective and matching contributions	$ 16,747	$ 16,581	$ 16,296
Increase (decrease) benefit plan exceed projected benefit obligation	405
Fair Value of Plan Assets for Plans with Benefit Obligations in Excess of Plan Assets	21,993
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) benefit plan exceed projected benefit obligation	(34,824)	(33,877)
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	8,500
Domestic Plan [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Gain (loss) due to settlements and curtailments	0	0	0
Defined Benefit Plan, Accumulated Benefit Obligation	315,698	303,446
Increase (decrease) benefit plan exceed projected benefit obligation	(39,931)	(49,963)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	0
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) benefit plan exceed projected benefit obligation	(24,242)	(18,350)
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	6,210
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Gain (loss) due to settlements and curtailments	(6,427)	(538)	$ (132)
Defined Benefit Plan, Accumulated Benefit Obligation	185,179	179,854
Increase (decrease) benefit plan exceed projected benefit obligation	(145,143)	(127,964)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	20,667	$ 1,950
UNITED KINGDOM | Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Gain (loss) due to settlements and curtailments	(5,717)
Other General and Administrative Expense	185
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 17,100