Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 87,412	$ 60,529	$ 180,055	$ 57,090
Unrealized gains and losses on debt securities:
Change in unrealized holding gains and losses, net	76,335	84,885	(122,703)	249,001
Less: Reclassification adjustment for gains included in net income	(1,300)	(4,006)	(4,020)	(5,233)
Change in unrealized gains and losses on debt securities during the period	75,035	80,879	(126,723)	243,768
Unrealized gains and losses on derivative hedges:
Change in unrealized gains and losses on derivative hedges	(3,422)	4,612	3,081	19,137
Less: Reclassification adjustment for (gains) losses included in net income	(877)	(514)	(1,719)	254
Change in unrealized gains and losses on derivative hedges	(4,299)	4,098	1,362	19,391
Other comprehensive income (loss), before tax	70,736	84,977	(125,361)	263,159
Income tax (expense) benefit	(16,826)	(20,105)	30,128	(62,077)
Other comprehensive income (loss)	53,910	64,872	(95,233)	201,082
Comprehensive income	$ 141,322	$ 125,401	$ 84,822	$ 258,172