Reclassifications of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes		$ 178,719	$ 189,065	$ 561,612	$ 566,816
Income tax expense (Benefit)		$ (64,031)	$ (68,807)	(203,961)	$ (212,616)
Total reclassifications for the period	[1]			(3,625)
Reclassification out of Accumulated Other Comprehensive Income (loss) | Amortization of defined benefit pension
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Past-service liability	[1],[2]			187
Actuarial losses	[1],[2]			(6,443)
Income before income taxes	[1]			(6,256)
Income tax expense (Benefit)	[1]			$ 2,631

[1] Amounts in parentheses indicate expense items.

[2] Please see Note 9, "Pension and Other Post-Retirement Benefits," for additional information.