CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (35,338)	$ 50,072	$ 79,589
Amounts related to available-for-sale securities:
Change in net unrealized gain or loss	71,148	(72,490)	(60,391)
Reclassification adjustment for amounts included in net (loss) income	1,365
Amounts related to cash flow hedges:
Change in net unrealized gain or loss	(17,080)	25,716	21,426
Reclassification adjustment for amounts included in net (loss) income	(20,988)	(36,390)	(4,808)
Other comprehensive income (loss)	34,445	(83,164)	(43,773)
Comprehensive (loss) income	$ (893)	$ (33,092)	$ 35,816