Other Noninterest Income and Other Noninterest Expense (Components of Other Noninterest Income and Other Noninterest Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other noninterest income:
Income from bank-owned life insurance	$ 11,473	$ 13,596	$ 10,881
Credit-related fees	11,140	9,926	11,057
Income from derivatives	5,870	5,196	2,745
Gain on sales of assets	7,478	7,814	186
Other miscellaneous income	13,814	10,950	11,092
Total other noninterest income	49,775	47,482	35,961
Other noninterest expense:
Advertising	15,031	10,938	11,225
Ad valorem and franchise taxes	12,797	8,741	10,498
Printing and supplies	5,139	4,422	4,851
Travel	5,043	4,268	5,331
Entertainment and contributions	8,260	7,122	6,723
Tax credit investment amortization	4,850	4,263	8,513
Loss share agreement termination	6,603
Other miscellaneous expense	24,913	32,810	25,062
Total other noninterest expense	$ 82,636	$ 72,564	$ 72,203