Deposits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deposits [Abstract]
Interest-bearing Domestic Deposit, Brokered	$ 0	$ 0
Deposits, by Type [Abstract]
Non-interest bearing demand	1,823,716	1,791,364
Interest bearing:
Demand	2,178,373	2,133,273
Savings	1,955,256	1,843,355
Time, $100 and over	487,372	520,125
Time, other	644,220	718,095
Total interest bearing	5,265,221	5,214,848
Total deposits	7,088,937	7,006,212
Time deposits obtained through Certificate of Deposit Account Registry Service (CDARS)	38,336	40,491
Contractual Maturities, Time Deposits, $100,000 or More [Abstract]
2015, Time, $100 and Over	109,343
2016, Time, $100 and Over	82,059
2017, Time, $100 and Over	131,381
2018, Time, $100 and Over	164,589
Time Deposits, $100,000 or More	487,372	520,125
Time Deposits, Fiscal Year Maturity [Abstract]
2015, Time	309,819
2016, Time	161,333
2017, Time	266,174
2018, Time	394,266
Time Deposits	1,131,592
Interest expense, time deposits, $100,000 or more	3,739	4,003	$ 4,880
Time Deposits, $250,000 or More	222,912	$ 228,410
FDIC Deposit Insurance Limit	$ 250