Changes in Accumulated Other Comprehensive (Loss) Earnings, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 4,060,177
Other comprehensive (loss) earnings before reclassifications, net of tax	$ (198)	$ (1,757)	(4,145)	$ (14,661)
Amounts reclassified from accumulated other comprehensive earnings, net of tax	1,755	1,829	5,256	8,078
Other comprehensive earnings (loss), net of tax	1,557	72	1,111	(6,583)
Ending Balance	4,158,398	4,252,580	4,158,398	4,252,580
Pension and Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(104,114)	(111,663)	(103,380)	(106,688)
Other comprehensive (loss) earnings before reclassifications, net of tax			(3,830)	(10,845)
Amounts reclassified from accumulated other comprehensive earnings, net of tax	1,547	1,636	4,643	7,506
Other comprehensive earnings (loss), net of tax	1,547	1,636	813	(3,339)
Ending Balance	(102,567)	(110,027)	(102,567)	(110,027)
Foreign Currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(381)	1,219	(264)	3,278
Other comprehensive (loss) earnings before reclassifications, net of tax	(198)	(1,757)	(315)	(3,816)
Other comprehensive earnings (loss), net of tax	(198)	(1,757)	(315)	(3,816)
Ending Balance	(579)	(538)	(579)	(538)
Unamortized Value of Terminated Forward Starting Interest Rate Swap
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,573)	(2,370)	(1,978)	(2,749)
Amounts reclassified from accumulated other comprehensive earnings, net of tax	208	193	613	572
Other comprehensive earnings (loss), net of tax	208	193	613	572
Ending Balance	(1,365)	(2,177)	(1,365)	(2,177)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(106,068)	(112,814)	(105,622)	(106,159)
Ending Balance	$ (104,511)	$ (112,742)	$ (104,511)	$ (112,742)