Changes in Cumulative Other Comprehensive Loss by Component - Changes in Cumulative Other Comprehensive Loss by Component (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (509,767)
Ending balance	(506,937)
Cumulative Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(22,034)	$ 9,059
Other comprehensive income (loss) before reclassifications	(2,754)	(11,758)
Net current-period other comprehensive income (loss)	(2,754)	(11,758)
Ending balance	(24,788)	(2,699)
Changes in the Fair Value of Derivatives and Unrealized Gains (Losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	3,454	4,762
Other comprehensive income (loss) before reclassifications	(2,487)	5,492
Amount reclassified from accumulated other comprehensive income (loss)	(896)	(2,804)
Net current-period other comprehensive income (loss)	(3,383)	2,688
Ending balance	71	7,450
Unrecognized Postretirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(491,187)	(544,423)
Other comprehensive income (loss) before reclassifications	2,029	5,227
Amount reclassified from accumulated other comprehensive income (loss)	6,938	7,467
Net current-period other comprehensive income (loss)	8,967	12,694
Ending balance	(482,220)	(531,729)
Cumulative Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(509,767)	(530,602)
Other comprehensive income (loss) before reclassifications	(3,212)	(1,039)
Amount reclassified from accumulated other comprehensive income (loss)	6,042	4,663
Net current-period other comprehensive income (loss)	2,830	3,624
Ending balance	$ (506,937)	$ (526,978)