Accumulated Other Comprehensive Income (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), Net of Tax [Roll Forward]
Beginning Balance	$ (82,457)	$ (55,237)	$ (84,983)	$ (57,190)
Other comprehensive income (loss) before reclassifications	2,095	1,411	7,559	5,439
Amounts reclassified from accumulated other comprehensive loss(1)	(1,468)	(927)	(4,406)	(3,002)
Net current-period other comprehensive income (loss)	627	484	3,153	2,437
Ending Balance	(81,830)	(54,753)	(81,830)	(54,753)
Changes in Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	0	118	87	423
Other comprehensive income (loss) before reclassifications	0	(16)	(87)	(101)
Amounts reclassified from accumulated other comprehensive loss(1)	0	0	0	(220)
Net current-period other comprehensive income (loss)	0	(16)	(87)	(321)
Ending Balance	0	102	0	102
Pension and Other Postretirement Benefits Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(80,905)	(55,687)	(83,879)	(57,224)
Other comprehensive income (loss) before reclassifications	2,903	1,857	8,815	5,249
Amounts reclassified from accumulated other comprehensive loss(1)	(1,468)	(927)	(4,406)	(2,782)
Net current-period other comprehensive income (loss)	1,435	930	4,409	2,467
Ending Balance	(79,470)	(54,757)	(79,470)	(54,757)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(1,552)	332	(1,191)	(389)
Other comprehensive income (loss) before reclassifications	(808)	(430)	(1,169)	291
Amounts reclassified from accumulated other comprehensive loss(1)	0	0	0	0
Net current-period other comprehensive income (loss)	(808)	(430)	(1,169)	291
Ending Balance	$ (2,360)	$ (98)	$ (2,360)	$ (98)