CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (63,460)	$ 12,988	$ (71,206)	$ 32,408
Amounts related to available-for-sale securities:
Change in net unrealized gains (losses)	48,550	(16,512)	92,026	(60,565)
Amounts related to cash flow hedges:
Change in net unrealized (losses) gains	(6,746)	7,873	(15,297)	38,805
Reclassification adjustment for amounts included in net income	(6,351)	(9,971)	(16,922)	(14,614)
Other comprehensive income	35,453	(18,610)	59,807	(36,374)
Comprehensive loss	$ (28,007)	$ (5,622)	$ (11,399)	$ (3,966)

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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