Pensions - Schedule of Defined Benefit Pension Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plans' assets at beginning of period	$ 316,703
Fair value of plans' assets at end of period	327,793	$ 316,703
Funded status of the plans	405
Domestic Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligations at beginning of year	33,877	33,955
Service cost	314	361	$ 434
Interest cost	1,297	1,383	1,411
Actuarial loss (gain)	1,021	112
Defined Benefit Plan, Benefit Obligation, Benefits Paid	1,690	1,939
Foreign currency exchange rate effect	0	0
Benefit obligation at end of year	34,824	33,877	33,955
Funded status of the plans	(34,824)	(33,877)
Foreign Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligations at beginning of year	18,350	16,455
Service cost	423	372	380
Interest cost	693	678	678
Actuarial loss (gain)	4,002	926
Defined Benefit Plan, Benefit Obligation, Benefits Paid	651	601
Foreign currency exchange rate effect	1,425	520
Benefit obligation at end of year	24,242	18,350	16,455
Funded status of the plans	(24,242)	(18,350)
Pension Plan [Member] | Domestic Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligations at beginning of year	303,446	306,760
Service cost	814	807	926
Interest cost	11,700	12,580	12,334
Actuarial loss (gain)	17,230	3,633
Defined Benefit Plan, Benefit Obligation, Benefits Paid	17,492	20,334
Foreign currency exchange rate effect	0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	0
Other	0	0
Benefit obligation at end of year	315,698	303,446	306,760
Fair value of plans' assets at beginning of period	253,483	248,387
Actual return on plans' assets	35,233	18,109
Employer contributions	4,543	7,321
Defined Benefit Plan, Plan Assets, Benefits Paid	17,492	20,334
Foreign currency exchange rate effect	0	0
Settlements	0	0
Fair value of plans' assets at end of period	275,767	253,483	248,387
Funded status of the plans	(39,931)	(49,963)
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligations at beginning of year	191,184	179,896
Service cost	4,025	3,346	3,489
Interest cost	4,341	5,041	5,084
Actuarial loss (gain)	4,450	17,582
Defined Benefit Plan, Benefit Obligation, Benefits Paid	7,048	7,735
Foreign currency exchange rate effect	20,809	(5,085)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	20,667	1,950
Other	75	89
Benefit obligation at end of year	197,169	191,184	179,896
Fair value of plans' assets at beginning of period	63,220	64,940
Actual return on plans' assets	5,039	2,560
Employer contributions	7,238	6,969
Defined Benefit Plan, Plan Assets, Benefits Paid	7,048	7,735
Foreign currency exchange rate effect	4,008	(1,753)
Settlements	(20,431)	(1,761)
Fair value of plans' assets at end of period	52,026	63,220	$ 64,940
Funded status of the plans	$ (145,143)	$ (127,964)