Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 243,600	$ 195,513	$ 247,105
Unrealized gains and losses on debt securities:
Change in unrealized holding gains and losses, net		253,891	(51,271)	21,139
Less: Reclassification adjustment for gains included in net income		(3,218)	(578)	(4,192)
Change in unrealized gains and losses on debt securities during the period		250,673	(51,849)	16,947
Unrealized gains and losses on derivative hedges:
Change in unrealized gains and losses on derivative hedges		(15,318)	1,906	(1,050)
Less: Reclassification adjustment for losses included in net income		1,023
Change in unrealized gains and losses on derivative hedges		(14,295)	1,906	(1,050)
Other comprehensive income (loss), before tax		236,378	(49,943)	15,897
Income tax (expense) benefit		(57,416)	12,735	(3,880)
Other comprehensive income (loss) before reclassifications		178,962	(37,208)	12,017
Amounts reclassified from accumulated other comprehensive income	[1],[2]		(13,049)
Net current-period other comprehensive income (loss)		178,962	(50,257)	12,017
Comprehensive income		$ 422,562	$ 145,256	$ 259,122

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

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