Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 57,849	$ 48,142	$ 170,059	$ 135,144
Unrealized gains and losses on debt securities:
Change in unrealized holding gains and losses, net		(36,331)	5,064	(133,013)	62,646
Less: Reclassification adjustment for gains included in net income		(211)	(2,390)	(578)	(4,138)
Change in unrealized gains and losses on debt securities during the period		(36,542)	2,674	(133,591)	58,508
Change in unrealized gains and losses on derivative hedges		1,162	(169)	4,274	(1,080)
Income tax benefit (expense)		8,698	(1,548)	32,250	(22,554)
Other comprehensive (loss) income before reclassifications		(26,682)	957	(97,067)	34,874
Amounts reclassified from accumulated other comprehensive income	[1],[2]			(13,049)
Net current-period other comprehensive (loss) income		(26,682)	957	(110,116)	34,874
Comprehensive income		$ 31,167	$ 49,099	$ 59,943	$ 170,018

[1] See Note 3, “New Accounting Pronouncements,” for discussion of the Company’s adoption of ASU No. 2018-02.

[2] See Note 3, “New Accounting Pronouncements,” for discussion of the Company’s adoption of Accounting Standards Update (ASU) No. 2016-01.