Accounting Policies - Reclassifications Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Other income (expense), net	$ 1,201	$ (443)	$ 5,958	$ 5,304
Income tax expense	(16,598)	(12,746)	(53,225)	(64,776)
Interest expense, net	(23,713)	(20,038)	(75,917)	(57,460)
Net income	87,739	67,399	260,521	213,313
Reclassification out of Accumulated Other Comprehensive Income | Pension and post retirement benefit plans
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Other income (expense), net	718	818	2,152	2,454
Income tax expense	(198)	(226)	(594)	(678)
Net income	520	592	1,558	1,776
Reclassification out of Accumulated Other Comprehensive Income | Amortization of initial net obligation and prior service cost
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Other income (expense), net	(375)	(422)	(1,126)	(1,266)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of net loss
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Other income (expense), net	1,093	1,240	3,278	3,720
Reclassification out of Accumulated Other Comprehensive Income | Derivative contracts
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Income tax expense	(1,180)	(131)	(1,456)	(447)
Interest expense, net	4,915	497	5,770	1,653
Net income	$ 3,735	$ 366	$ 4,314	$ 1,206