Changes in Cumulative Other Comprehensive Loss by Component - Changes in Cumulative Other Comprehensive Loss by Component (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivatives (Effective Portion)	$ 3,210		$ 5,242
Amount of gain recognized in other comprehensive loss, net tax	1,182		2,173
Amount of gain reclassified from Cumulative Other Comprehensive Loss	944		449
Amount of gain reclassified from Cumulative Other Comprehensive Loss, net of tax	379		231
Amortization of prior service credit	142	172	284	528
Amortization of actuarial loss	(12,469)	(11,620)	(24,948)	(23,403)
Income tax provision on postretirement benefit plans	$ 4,577	$ 4,223	$ 9,166	$ 8,378

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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Before tax amount of the income statement impact of the reclassification adjustment for prior service costs recognized as a component of net period benefit cost.

+ References

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+ Details

- Definition

Before tax amount of the income statement impact of the reclassification adjustment of accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges realized in net income. Also includes reclassification adjustments of an entity's share of an equity investee's deferred hedging gain (loss) realized in net income.

+ References

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+ Details

- Definition

Tax effect of the income statement impact of the reclassification adjustment of accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges realized in net income. Also includes reclassification adjustments of an entity's share of an equity investee's deferred hedging gain (loss) realized in net income.

+ References+ Details