Condensed Parent Company Financial Statements - Statements of Income (Parent Company Only) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income
Interest income	$ 582,492	$ 509,716	$ 378,332
Securities transactions and other	9,636	9,859	7,282
Expenses
Interest expense	65,870	37,712	28,641
Other expenses	28,236	23,956	20,152
Income before income tax expense	197,057	187,954	138,520
Income tax benefit	(39,187)	(89,567)	(46,171)
Net income	157,870	98,387	92,349
Net income applicable to non-vested restricted shares	(1,312)	(916)	(1,043)
Net income applicable to common shares	156,558	97,471	91,306
Parent Company
Income
Dividends from subsidiaries	86,095	74,091	86,791
Interest income	453	2,211	2,188
Securities transactions and other	280	(1,372)	215
Total income	86,828	74,930	89,194
Expenses
Interest expense	12,708	12,428	12,477
Salaries and employee benefits	22,430	20,978	16,104
Other expenses	9,440	9,126	7,110
Total expenses	44,578	42,532	35,691
Income before income tax expense	42,250	32,398	53,503
Income tax benefit	13,299	14,851	12,878
Income before equity in undistributed income of subsidiaries	55,549	47,249	66,381
Equity in undistributed income of subsidiaries	102,321	51,138	25,968
Net income	157,870	98,387	92,349
Net income applicable to non-vested restricted shares	(1,312)	(916)	(1,043)
Net income applicable to common shares	$ 156,558	$ 97,471	$ 91,306