Merger - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Combinations [Abstract]
Net interest income and other noninterest income	$ 2,225,244	$ 2,228,154	$ 2,086,745
Net income	587,335	590,594	432,128
Net income available to common shareholders	$ 577,360	$ 575,525	$ 406,445
Earnings per share:
Basic (in usd per share)	$ 3.77	$ 3.70	$ 2.61
Diluted (in usd per share)	$ 3.75	$ 3.67	$ 2.60