Securities (Details) - Securities Portfolio - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	$ 22,291	$ 23,152
Fair Value	18,212	20,054
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	17,920	16,894
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	1,957,584	1,324,146
Gross Unrealized Gains	4,562	9,921
Gross Unrealized Losses	(42,696)	(27,431)
Fair Value	1,919,450	1,306,636
U.S. treasury securities
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	48,581	17,000
Gross Unrealized Gains	26	15
Gross Unrealized Losses	(66)	(35)
Fair Value	48,541	16,980
U.S. agency securities
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	183,528	86,461
Gross Unrealized Gains	519	351
Gross Unrealized Losses	(410)	(169)
Fair Value	183,637	86,643
Collateralized mortgage obligations (CMOs)
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	1,064,130	695,198
Gross Unrealized Gains	969	1,072
Gross Unrealized Losses	(17,653)	(9,085)
Fair Value	1,047,446	687,185
Other mortgage-backed securities (MBSs)
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	337,139	152,481
Gross Unrealized Gains	1,395	1,920
Gross Unrealized Losses	(5,879)	(871)
Fair Value	332,655	153,530
Municipal securities
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	273,319	321,437
Gross Unrealized Gains	1,245	6,443
Gross Unrealized Losses	(3,718)	(310)
Fair Value	270,846	327,570
Trust-preferred collateralized debt obligations (CDOs)
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	47,681	48,287
Gross Unrealized Gains	261	34
Gross Unrealized Losses	(14,682)	(16,792)
Fair Value	33,260	31,529
Equity securities
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	3,206	3,282
Gross Unrealized Gains	147	86
Gross Unrealized Losses	(288)	(169)
Fair Value	3,065	3,199
Trading securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities	17,920	16,894
Municipal securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	22,291	23,152
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4,079)	(3,098)
Fair Value	$ 18,212	$ 20,054

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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