CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ (114,852)us-gaap_NetIncomeLoss	$ 252,576us-gaap_NetIncomeLoss	$ 180,602us-gaap_NetIncomeLoss
OTHER COMPREHENSIVE INCOME (LOSS)
Net changes in pension and other postretirement plan assets and benefit obligations recognized in other comprehensive income, net of income tax (benefit) expense of ($46,944), $34,092, and ($8,003), respectively	(87,293)	63,315	(14,862)
Net reclassification adjustments for amounts recognized in net income as a component of net periodic benefit cost, net of income tax expense of $5,261, $8,250, and $10,474, respectively	9,824	15,322	19,451
OTHER COMPREHENSIVE INCOME	(77,469)	78,637	4,589
COMPREHENSIVE INCOME (LOSS)	$ (192,321)	$ 331,213	$ 185,191

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax, before reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement benefit plans.

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Amount after tax and reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

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