Changes in Accumulated Other Comprehensive Loss by Component - Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ 1,185,756
Other comprehensive income (loss) before reclassifications	$ (28,706)	$ 10,541	(7,135)	$ 22,669
Foreign currency translation effect	4,082	(3,702)	1,180	(4,567)
Income tax effect	(285)	759	(701)	908
Amount reclassified from accumulated other comprehensive loss
Cash flow hedges	(1,592)	(343)	(98)	(353)
Amortization of prior service credit	(135)	(142)	(270)	(283)
Amortization of actuarial loss	9,320	10,631	18,666	21,222
Pension settlement charge			0	0
Income tax effect	(2,080)	(3,526)	(4,462)	(7,241)
Other comprehensive income (loss)	(19,396)	14,218	7,180	32,355
Ending Balance	1,177,268		1,177,268
Cumulative Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(19,015)	(62,898)	(39,940)	(75,415)
Other comprehensive income (loss) before reclassifications	(30,768)	12,876	(9,843)	25,393
Amount reclassified from accumulated other comprehensive loss
Other comprehensive income (loss)	(30,768)	12,876	(9,843)	25,393
Ending Balance	(49,783)	(50,022)	(49,783)	(50,022)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	1,901	1,721	349	1,967
Other comprehensive income (loss) before reclassifications	2,062	(2,335)	2,708	(2,724)
Income tax effect	(285)	759	(701)	908
Amount reclassified from accumulated other comprehensive loss
Cash flow hedges	(1,592)	(343)	(98)	(353)
Income tax effect	126	199	(46)	203
Other comprehensive income (loss)	311	(1,720)	1,863	(1,966)
Ending Balance	2,212	1	2,212	1
Post-retirement Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(434,788)	(465,837)	(438,887)	(471,703)
Other comprehensive income (loss) before reclassifications		0		0
Foreign currency translation effect	4,082	(3,702)	1,180	(4,567)
Income tax effect		0		0
Amount reclassified from accumulated other comprehensive loss
Amortization of prior service credit	(135)	(142)	(270)	(283)
Amortization of actuarial loss	9,320	10,631	18,666	21,222
Pension settlement charge			0	0
Income tax effect	(2,206)	(3,725)	(4,416)	(7,444)
Other comprehensive income (loss)	11,061	3,062	15,160	8,928
Ending Balance	(423,727)	(462,775)	(423,727)	(462,775)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(451,902)	(527,014)	(478,478)	(545,151)
Amount reclassified from accumulated other comprehensive loss
Ending Balance	$ (471,298)	$ (512,796)	$ (471,298)	$ (512,796)