Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 286,502	$ 243,600	$ 195,513
Unrealized gains and losses on debt securities:
Change in unrealized holding gains and losses, net		295,552	253,891	(51,271)
Less: Reclassification adjustment for gains included in net income		(6,980)	(3,218)	(578)
Change in unrealized gains and losses on debt securities during the period		288,572	250,673	(51,849)
Unrealized gains and losses on derivative hedges:
Change in unrealized gains and losses on derivative hedges		20,979	(15,318)	1,906
Less: Reclassification adjustment for (gains) losses included in net income		(1,905)	1,023
Change in unrealized gains and losses on derivative hedges		19,074	(14,295)	1,906
Other comprehensive income (loss), before tax		307,646	236,378	(49,943)
Income tax (expense) benefit		(72,486)	(57,416)	12,735
Other comprehensive income (loss) before reclassifications		235,160	178,962	(37,208)
Amounts reclassified from accumulated other comprehensive income	[1],[2]			(13,049)
Net current-period other comprehensive income (loss)		235,160	178,962	(50,257)
Comprehensive income		$ 521,662	$ 422,562	$ 145,256

[1] See Note 2, “New Accounting Pronouncements,” for discussion of the Company’s adoption of ASU No. 2018-02.

[2] See Note 2, “New Accounting Pronouncements,” for discussions of the Company’s adoption of ASU No. 2016-01.