Reclassifications of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	$ 188,159		$ 189,690	$ 189,690
Income tax expense (Benefit)	(68,900)		(74,436)	(74,436)
Total reclassifications for the period	(1,244)	[1]
Reclassification out of Accumulated Other Comprehensive Income (loss) | Amortization of defined benefit pension
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs	62	[1],[2]
Actuarial losses	(2,148)	[1],[2]
Income before income taxes	(2,086)	[1]
Income tax expense (Benefit)	$ 842	[1]

[1] Amounts in parentheses indicate expense items.

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