Condensed Parent Company Financial Statements (Details) - Statements of Income (Parent Company Only) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income
Interest income	$ 378,332	$ 335,984	$ 299,864
Securities transactions and other	3,635	2,764	4,567
Expenses
Interest expense	28,641	24,386	23,012
Other expenses	24,834	21,601	20,135
Income before income tax expense	138,520	119,811	100,476
Income tax benefit	(46,171)	(37,747)	(31,170)
Net income	92,349	82,064	69,306
Net income applicable to non-vested restricted shares	(1,043)	(882)	(836)
Net income applicable to common shares	91,306	81,182	68,470
Parent Company
Income
Dividends from subsidiaries	86,791	127,000	56,881
Interest income	2,188	2,164	1,502
Securities transactions and other	215	584	6,451
Total income	89,194	129,748	64,834
Expenses
Interest expense	12,477	12,545	12,062
Salaries and employee benefits	16,104	14,624	12,589
Other expenses	7,110	6,003	5,867
Total expenses	35,691	33,172	30,518
Income before income tax expense	53,503	96,576	34,316
Income tax benefit	12,878	11,950	8,710
Income before equity in undistributed (loss) income of subsidiaries	66,381	108,526	43,026
Equity in undistributed income (loss) of subsidiaries	25,968	(26,462)	26,280
Net income	92,349	82,064	69,306
Net income applicable to non-vested restricted shares	(1,043)	(882)	(836)
Net income applicable to common shares	$ 91,306	$ 81,182	$ 68,470