Securities (Details) - Securities Portfolio - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Securities Available-for-Sale
Amortized Cost	$ 1,157,534	$ 1,192,322
Gross Unrealized Gains	14,402	17,922
Gross Unrealized Losses	(20,518)	(23,235)
Fair Value	1,151,418	1,187,009
Securities Held-to-Maturity
Amortized Cost	23,723	26,555
Municipal securities, Gross Unrealized Gains	0	1,115
Municipal securities, Gross Unrealized Losses	(15)	0
Municipal securities, Fair Value	23,708	27,670
Trading Securities	17,038	17,460
US Treasury Securities
Securities Available-for-Sale
Amortized Cost	1,999	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	1,999	0
U.S. Agency Securities
Securities Available-for-Sale
Amortized Cost	18,289	30,297
Gross Unrealized Gains	337	144
Gross Unrealized Losses	(3)	(10)
Fair Value	18,623	30,431
Collateralized Mortgage Obligations
Securities Available-for-Sale
Amortized Cost	545,992	538,882
Gross Unrealized Gains	3,765	2,256
Gross Unrealized Losses	(3,282)	(6,982)
Fair Value	546,475	534,156
Other Mortgage Backed Securities
Securities Available-for-Sale
Amortized Cost	164,326	155,443
Gross Unrealized Gains	3,290	4,632
Gross Unrealized Losses	(235)	(310)
Fair Value	167,381	159,765
Municipal Securities
Securities Available-for-Sale
Amortized Cost	375,323	414,255
Gross Unrealized Gains	6,880	10,583
Gross Unrealized Losses	(649)	(1,018)
Fair Value	381,554	423,820
Trust-preferred collateralized debt obligations
Securities Available-for-Sale
Amortized Cost	48,159	48,502
Gross Unrealized Gains	37	152
Gross Unrealized Losses	(16,326)	(14,880)
Fair Value	31,870	33,774
Corporate Debt Securities
Securities Available-for-Sale
Amortized Cost	0	1,719
Gross Unrealized Gains	0	83
Gross Unrealized Losses	0	0
Fair Value	0	1,802
Equity Securities
Securities Available-for-Sale
Amortized Cost	3,446	3,224
Gross Unrealized Gains	93	72
Gross Unrealized Losses	(23)	(35)
Fair Value	$ 3,516	$ 3,261

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