Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (20,719)	$ 536,112	$ 319,361
Available for sale securities:
Change in net unrealized (losses) gains	(3,285)	996	(2,080)
Less: reclassification adjustment for net (gains) losses included in net income	(273)	(1,204)	170
Net change (net of tax effect)	(3,558)	(208)	(1,910)
Gain on pension liability	2,768	906	4,083
Cash flow hedges:
Change in unrealized gains (losses)	6,046	(2,638)	(6,937)
Less: reclassification adjustment for net (gains) losses included in net income	(758)	1,763	13,027
Net change (net of tax effect)	5,288	(875)	6,090
Other comprehensive income (loss)	4,498	(177)	8,263
Comprehensive (loss) income	$ (16,221)	$ 535,935	$ 327,624

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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