Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (73,328)	$ 19,321
Derivative financial instruments:
Reclassification adjustment for gain included in net (loss) income	(1)	(2)
Investments in marketable securities:
Unrealized holding gain	14
Reclassification adjustment for gain included in net (loss) income	(32)
Total other comprehensive loss	(19)	(2)
Comprehensive (loss) income	$ (73,347)	$ 19,319

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 of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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