Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 73,092	$ 62,382	$ 130,182	$ 177,085
Unrealized gains and losses on debt securities:
Change in unrealized holding gains and losses, net	20,975	54,182	269,976	268,100
Less: Reclassification adjustment for gains included in net income	(311)	(3,057)	(5,544)	(2,463)
Change in unrealized gains and losses on debt securities during the period	20,664	51,125	264,432	265,637
Unrealized gains and losses on derivative hedges:
Change in unrealized gains and losses on derivative hedges	(122)	(7,469)	19,015	(12,618)
Less: Reclassification adjustment for (gains) losses included in net income	(1,123)	280	(869)	295
Change in unrealized gains and losses on derivative hedges	(1,245)	(7,189)	18,146	(12,323)
Other comprehensive income, before tax	19,419	43,936	282,578	253,314
Income tax expense	(4,578)	(10,532)	(66,655)	(61,511)
Other comprehensive income	14,841	33,404	215,923	191,803
Comprehensive income	$ 87,933	$ 95,786	$ 346,105	$ 368,888