Cumulative Other Comprehensive Loss - Cumulative Other Comprehensive Loss in Accompanying Consolidated Statements of Equity (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending balance	$ (530,602)	$ (410,020)
Cumulative Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	59,660	44,135
Other comprehensive income (loss) before reclassifications	(50,601)	15,525
Net current-period other comprehensive income (loss)	(50,601)	15,525
Ending balance	9,059	59,660
Changes in the Fair Value of Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,615	427
Other comprehensive income (loss) before reclassifications	5,626	1,727
Amount reclassified from accumulated other comprehensive loss	(2,479)	(539)
Net current-period other comprehensive income (loss)	3,147	1,188
Ending balance	4,762	1,615
Unrecognized Postretirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(471,295)	(596,088)
Other comprehensive income (loss) before reclassifications	(96,737)	91,506
Amount reclassified from accumulated other comprehensive loss	23,609	33,287
Net current-period other comprehensive income (loss)	(73,128)	124,793
Ending balance	(544,423)	(471,295)
Cumulative Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(410,020)	(551,526)
Other comprehensive income (loss) before reclassifications	(141,712)	108,758
Amount reclassified from accumulated other comprehensive loss	21,130	32,748
Net current-period other comprehensive income (loss)	(120,582)	141,506
Ending balance	$ (530,602)	$ (410,020)