Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 57,744	$ 56,786
Unrealized gains and losses on debt securities:
Change in unrealized holding gains and losses, net		106,434	(80,662)
Less: Reclassification adjustment for gains included in net income		(809)	(139)
Change in unrealized gains and losses on debt securities during the period		105,625	(80,801)
Change in unrealized gains and losses on derivative hedges		(2,093)	2,202
Income tax (expense) benefit		(25,389)	19,782
Other comprehensive income (loss) before reclassifications		78,143	(58,817)
Amounts reclassified from accumulated other comprehensive income	[1],[2]		(13,049)
Net current-period other comprehensive income (loss)		78,143	(71,866)
Comprehensive income (loss)		$ 135,887	$ (15,080)

[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.