Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (3,439)	$ 57,744
Unrealized gains and losses on debt securities:
Change in unrealized holding gains and losses, net	164,116	106,434
Less: Reclassification adjustment for gains included in net income	(1,227)	(809)
Change in unrealized gains and losses on debt securities during the period	162,889	105,625
Unrealized gains and losses on derivative hedges:
Change in unrealized gains and losses on derivative hedges	14,525	(2,088)
Less: Reclassification adjustment for losses (gains) included in net income	768	(5)
Change in unrealized gains and losses on derivative hedges	15,293	(2,093)
Other comprehensive income, before tax	178,182	103,532
Income tax expense	(41,972)	(25,389)
Other comprehensive income	136,210	78,143
Comprehensive income	$ 132,771	$ 135,887