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 Income And Comprehensive Income [Abstract]
Net income (loss)	$ 27,122us-gaap_NetIncomeLoss	$ 133,825us-gaap_NetIncomeLoss	$ 13,601us-gaap_NetIncomeLoss
Other comprehensive income (loss), net of tax:
Change in fair value of interest rate swap agreements	(2,372)	234	0
Total other comprehensive income (loss)	(2,372)	234
Comprehensive income (loss)	$ 24,750us-gaap_ComprehensiveIncomeNetOfTax	$ 134,059us-gaap_ComprehensiveIncomeNetOfTax	$ 13,601us-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 and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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

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