Condensed Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (23,059)	$ (3,490)	$ (32,840)	$ 19,593
Other comprehensive (loss) income, net of tax:
Net change in net unrealized (loss) gain on investments	167	22	(229)	50
Net change in unrealized (loss) gain on hedging instruments	(1,867)	419	(2,278)	2,148
Total other comprehensive (loss) income, net of tax	(1,700)	441	(2,507)	2,198
Comprehensive (loss) income	$ (24,759)	$ (3,049)	$ (35,347)	$ 21,791

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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