Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ 335,322
Balance at end of period	353,071
Other comprehensive income, net of tax	3,501	$ 980
Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	46,069	20,473
Change in accounting principle - ASU 2016-01	(46,069)
Balance at beginning of period, as adjusted		20,473
Other comprehensive income - unrealized gains (losses) arising during the year		(1,722)
Balance at end of period		18,751
Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(164,467)	(175,859)
Balance at end of period	(161,876)	(174,088)
Other comprehensive income (loss)	2,591	1,771
Interest Rate Swap
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(390)
Balance at end of period		(278)
Unrealized gains arising during the year		1
Less reclassification adjustment for amounts included in interest expense		111
Accumulated Defined Benefit Plans Adjustment | Defined Benefit Pension Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(72,951)	(76,710)
Balance at end of period	(71,968)	(75,843)
Other comprehensive income (loss)	983	867
Accumulated Defined Benefit Plans Adjustment | OPEB
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(388)	(360)
Balance at end of period	(461)	(408)
Other comprehensive income (loss)	(73)	(48)
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(191,737)	(232,846)
Change in accounting principle - ASU 2016-01	(46,069)
Balance at beginning of period, as adjusted	(237,806)	(232,846)
Balance at end of period	(234,305)	(231,866)
Other comprehensive income, net of tax	$ 3,501	$ 980