Accumulated Other Comprehensive Loss - Net Change and Ending Balances for Various Components of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (68,753)	$ (45,865)
Net Change	$ (739)	$ (2,358)	6,190	5,733
Ending balance	(62,563)	(40,132)	(62,563)	(40,132)
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(4,426)	277
Net Change			(2,065)	(1,945)
Ending balance	(6,491)	(1,668)	(6,491)	(1,668)
Unrecognized Employee Benefit Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(65,396)	(47,462)
Net Change			8,637	7,749
Ending balance	(56,759)	(39,713)	(56,759)	(39,713)
Unrealized Holding Gains (Losses) on Marketable Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			984	1,007
Net Change			(357)	54
Ending balance	627	1,061	627	1,061
Realized (Gains) Losses from Settlement of Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			85	313
Net Change			(25)	(125)
Ending balance	$ 60	$ 188	$ 60	$ 188