CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (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)	$ 29,253us-gaap_NetIncomeLoss	$ (27,024)us-gaap_NetIncomeLoss	$ 138,970us-gaap_NetIncomeLoss
Other comprehensive income (loss), net of tax:
Net actuarial pension (loss) gain, net of income tax of $683, $6,811 and $242	(1,077)	10,755	379
Net actuarial pension loss amortization, net of income tax of $0, $790 and $1,062	0	1,247	1,656
Prior service cost (credit) amortization, net of income tax of $603, $604 and $607	(952)	(951)	(948)
Pension settlement, net of income tax of $53, $17 and $309	84	25	483
Unrealized gains (losses) on available-for-sale securities, net of income tax of $0, $0 and $0	0	0	(21)
Other comprehensive income (loss), net of tax	(1,945)	11,076	1,549
Comprehensive income (loss)	$ 27,308us-gaap_ComprehensiveIncomeNetOfTax	$ (15,948)us-gaap_ComprehensiveIncomeNetOfTax	$ 140,519us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. 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 (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit.

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Amount after tax of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) related to pension and other postretirement benefit plans.

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Amount after tax of gain (loss) adjustment to other comprehensive income (loss) resulting from settlement or curtailment of defined benefit pension and other postretirement defined benefit plans.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustment from accumulated other comprehensive income (loss) for actuarial gain (loss) related to pension and other postretirement benefit plans.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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