Reclassifications Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Additional interest expense	$ 23,141	$ 20,568	$ 68,037	$ 60,896
Tax benefit	52,763	70,869	119,277	144,014
Earnings from Continuing Operations	2,140	1,755	6,395	5,256
Pension and Postretirement Benefit Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Earnings from Continuing Operations	1,918	1,547	5,738	4,643
Unamortized Value of Terminated Forward Starting Interest Rate Swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Earnings from Continuing Operations	222	208	657	613
Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement Benefit Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Settlement charge				59
Prior service credit	(402)	(404)	(1,070)	(1,209)
Actuarial loss	3,513	2,893	10,370	8,681
Tax benefit	(1,193)	(942)	(3,562)	(2,888)
Earnings from Continuing Operations	1,918	1,547	5,738	4,643
Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement Benefit Plans | Other Nonoperating Income, Net
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications out of accumulated other comprehensive loss before taxes	3,111	2,489	9,300	7,531
Reclassification out of Accumulated Other Comprehensive Income | Unamortized Value of Terminated Forward Starting Interest Rate Swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Additional interest expense	369	344	1,089	1,016
Tax benefit	(147)	(136)	(432)	(403)
Earnings from Continuing Operations	$ 222	$ 208	$ 657	$ 613