Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 3,721,525	$ 3,213,655
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	68,965	32,386
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(16,059)	(22,211)
Securities available-for-sale, at fair value	3,774,431	3,223,830
Government agency and government-sponsored enterprise pass through securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	243,375	499,185
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,743	6,222
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(844)	(2,964)
Securities available-for-sale, at fair value	246,274	502,443
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	277,638	145,258
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	968	1,528
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(2,897)	(497)
Securities available-for-sale, at fair value	275,709	146,289
Private Label Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	122,816	122,707
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,813	4,199
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(642)	(1,437)
Securities available-for-sale, at fair value	125,987	125,469
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,627,707	1,447,064
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	53,700	15,406
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,339)	(6,011)
Securities available-for-sale, at fair value	1,680,068	1,456,459
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,169,969	555,552
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,758	1,798
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(8,758)	(9,658)
Securities available-for-sale, at fair value	1,163,969	547,692
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	17,000	47,100
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,295	680
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	(271)
Securities available-for-sale, at fair value	19,295	47,509
Collateralized Loan Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	6,960	155,440
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	55	1,685
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	(238)
Securities available-for-sale, at fair value	7,015	156,887
SBA asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	160,214	179,085
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	695	510
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(575)	(750)
Securities available-for-sale, at fair value	160,334	178,845
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	95,846	62,264
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	938	358
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,004)	(385)
Securities available-for-sale, at fair value	$ 95,780	$ 62,237

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
-Paragraph 1
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