Reclassifications Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Additional interest expense	$ 24,045	$ 20,294	$ 44,896	$ 40,328
Tax benefit	51,986	53,435	66,514	73,145
Earnings from Continuing Operations	2,130	1,733	4,255	3,501
Pension and Postretirement Benefit Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Earnings from Continuing Operations	1,910	1,529	3,820	3,096
Unamortized Value of Terminated Forward Starting Interest Rate Swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Earnings from Continuing Operations	220	204	435	405
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	(358)	(518)	(716)	(806)
Actuarial loss	3,452	3,007	6,905	5,787
Tax benefit	(1,184)	(960)	(2,369)	(1,944)
Earnings from Continuing Operations	1,910	1,529	3,820	3,096
Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement Benefit Plans | Nonoperating Expenses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications out of accumulated other comprehensive loss before taxes	3,094	2,489	6,189	5,040
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	364	340	720	672
Tax benefit	(144)	(136)	(285)	(267)
Earnings from Continuing Operations	$ 220	$ 204	$ 435	$ 405