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)	$ 126,452us-gaap_NetIncomeLoss	$ 118,352us-gaap_NetIncomeLoss	$ (26,644)us-gaap_NetIncomeLoss
Other comprehensive income, before tax:
Unrealized gains (losses) arising during the period	(20,231)	23,172	14,451
Amount reclassified from accumulated OCI into income (expense)	(235)	204	3,601
Total Minimum pension liability	(20,466)	23,376	18,052
Income tax (expense) benefit related to items of comprehensive income	3,254us-gaap_OtherComprehensiveIncomeLossTax	(7,892)us-gaap_OtherComprehensiveIncomeLossTax	(6,624)us-gaap_OtherComprehensiveIncomeLossTax
Other comprehensive income (loss), net of tax	(17,212)	15,484	11,428
Comprehensive income (loss)	$ 109,240us-gaap_ComprehensiveIncomeNetOfTax	$ 133,836us-gaap_ComprehensiveIncomeNetOfTax	$ (15,216)us-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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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount before tax of reclassification adjustment from accumulated other comprehensive (income) loss related to net period benefit cost (credit) for pension and other postretirement defined benefit plans.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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