Condensed Financial Information (parent company only) - Statement of Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income
Gain on the sale of insurance subsidiary										$ 8,265
Gain on cancellation of subordinated debentures										1,250
Other income									3,594	1,778	1,854
Expenses
Interest expense	$ 6,631	$ 6,694	$ 6,742	$ 6,772	$ 6,440	$ 6,215	$ 6,171	$ 5,968	26,839	24,794	21,842
Salaries and employee benefits									102,552	101,908	96,499
Other expenses									15,470	15,187	14,236
INCOME BEFORE INCOME TAX	30,143	28,528	26,722	23,267	18,595	23,624	26,824	22,006
Income tax benefit (expense)	(7,850)	(7,469)	(6,716)	(5,574)	(4,418)	(6,557)	(8,856)	(5,834)	(27,609)	(25,665)	(22,123)
Net income available to common stockholders									81,051	65,384	60,162
Net income	$ 22,293	$ 21,059	$ 20,006	$ 17,693	$ 14,177	$ 17,067	$ 17,968	$ 16,172	81,051	65,384	60,162
Other comprehensive income (loss)									(12,219)	268	4,780
Comprehensive income									68,832	65,652	64,942
Parent
Income
Dividends from subsidiaries									33,546	39,032	53,231
Gain on the sale of insurance subsidiary										8,265
Gain on cancellation of subordinated debentures										1,250
Other income									143	197	538
Total income									33,689	48,744	53,769
Expenses
Interest expense									7,185	6,661	6,616
Salaries and employee benefits									639	3,023	3,128
Net occupancy and equipment expenses									832	464	442
Other outside services									967	1,455	458
Professional services									279	636	409
Other expenses									(470)	1,234	1,132
Total expenses									9,432	13,473	12,185
INCOME BEFORE INCOME TAX									24,257	35,271	41,584
Income tax benefit (expense)									3,243	(974)	3,999
Income before equity in undistributed income of subsidiaries									27,500	34,297	45,583
Equity in undistributed (distributions in excess of) income of subsidiaries									53,551	31,087	14,579
Net income available to common stockholders									81,051	65,384	60,162
Net income									81,051	65,384	60,162
Other comprehensive income (loss)									(12,219)	268	4,780
Comprehensive income									$ 68,832	$ 65,652	$ 64,942