Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 79,164	$ 72,475
Other comprehensive income/loss before income taxes:
Net change in unrealized gain/loss on securities available for sale and cash flow hedges	57,243	(62,244)
Reclassification of net losses realized and included in earnings	4,219	1,796
Amortization of unrealized net loss on securities transferred to held to maturity	591	755
Other comprehensive income/loss before income taxes	62,053	(59,693)
Income tax expense (benefit)	13,853	(13,546)
Other comprehensive income/loss net of income taxes	48,200	(46,147)
Comprehensive income	$ 127,364	$ 26,328