Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Components Of Other Comprehensive Income Loss [Line Items]
Balance at beginning of period			$ 149,950
Other comprehensive income (loss)	$ 9,590	$ (38,019)	14,278	$ (55,386)
Balance at end of period	170,109		170,109
Marketable Securities
Components Of Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	2,394	39,968	195	47,112
Other comprehensive income (loss)	6,983	(34,513)	9,182	(41,657)
Balance at end of period	9,377	5,455	9,377	5,455
Currency Translation
Components Of Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(170,533)	(165,944)	(172,384)	(154,173)
Other comprehensive income (loss)	1,777	(3,538)	3,628	(15,309)
Balance at end of period	(168,756)	(169,482)	(168,756)	(169,482)
Interest Rate Swap
Components Of Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(1,173)		(445)
Other comprehensive income (loss)	32	(733)	(920)	(733)
Less reclassification adjustment for amounts included in interest expense	113		337
Balance at end of period	(1,028)	(733)	(1,028)	(733)
Accumulated Defined Benefit Plans Adjustment | Defined Benefit Pension Plans
Components Of Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(71,082)	(73,439)	(72,712)	(75,260)
Other comprehensive income (loss)	817	902	2,447	2,723
Balance at end of period	(70,265)	(72,537)	(70,265)	(72,537)
Accumulated Defined Benefit Plans Adjustment | OPEB
Components Of Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(276)	9	(12)	282
Other comprehensive income (loss)	(132)	(137)	(396)	(410)
Balance at end of period	(408)	(128)	(408)	(128)
Total Accumulated Other Comprehensive Loss
Components Of Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(240,670)	(199,406)	(245,358)	(182,039)
Balance at end of period	$ (231,080)	$ (237,425)	$ (231,080)	$ (237,425)