Securities (Details) - Securities Portfolio - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Securities Available-for-Sale
Amortized Cost	$ 1,763,813	$ 1,324,146
Gross Unrealized Gains	29,160	9,921
Gross Unrealized Losses	(19,214)	(27,431)
Fair Value	1,773,759	1,306,636
Securities Held-to-Maturity
Amortized Cost	20,672	23,152
Municipal securities, Gross Unrealized Gains	0	0
Municipal securities, Gross Unrealized Losses	(2,278)	(3,098)
Municipal securities, Fair Value	18,394	20,054
Trading Securities	17,693	16,894
U.S. treasury securities
Securities Available-for-Sale
Amortized Cost	38,548	17,000
Gross Unrealized Gains	341	15
Gross Unrealized Losses	0	(35)
Fair Value	38,889	16,980
U.S. agency securities
Securities Available-for-Sale
Amortized Cost	196,735	86,461
Gross Unrealized Gains	2,580	351
Gross Unrealized Losses	(84)	(169)
Fair Value	199,231	86,643
Collateralized mortgage obligations (CMOs)
Securities Available-for-Sale
Amortized Cost	908,550	695,198
Gross Unrealized Gains	13,239	1,072
Gross Unrealized Losses	(1,054)	(9,085)
Fair Value	920,735	687,185
Other mortgage backed securities (MBSs)
Securities Available-for-Sale
Amortized Cost	281,924	152,481
Gross Unrealized Gains	4,839	1,920
Gross Unrealized Losses	(106)	(871)
Fair Value	286,657	153,530
Municipal securities
Securities Available-for-Sale
Amortized Cost	286,547	321,437
Gross Unrealized Gains	8,046	6,443
Gross Unrealized Losses	(29)	(310)
Fair Value	294,564	327,570
Trust-preferred collateralized debt obligations (CDOs)
Securities Available-for-Sale
Amortized Cost	48,219	48,287
Gross Unrealized Gains	32	34
Gross Unrealized Losses	(17,820)	(16,792)
Fair Value	30,431	31,529
Equity securities
Securities Available-for-Sale
Amortized Cost	3,290	3,282
Gross Unrealized Gains	83	86
Gross Unrealized Losses	(121)	(169)
Fair Value	$ 3,252	$ 3,199

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