Investment Securities (Details 1) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	$ 3,209,385	$ 3,512,385
Available-for-sale Securities, Gross Unrealized Gain	144,055	62,157
Available-for-sale Securities, Gross Unrealized Loss	(5,894)	(15,105)
Securities available‑for‑sale	3,347,546	3,559,437
Government agency and government-sponsored enterprise pass through securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	509,895	660,069
Available-for-sale Securities, Gross Unrealized Gain	11,108	11,517
Available-for-sale Securities, Gross Unrealized Loss	(484)	(3,746)
Securities available‑for‑sale	520,519	667,840
Government agency and government-sponsored enterprise collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	161,207	193,148
Available-for-sale Securities, Gross Unrealized Gain	4,158	2,633
Available-for-sale Securities, Gross Unrealized Loss	(154)	(1,026)
Securities available‑for‑sale	165,211	194,755
Private label collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	144,935	140,065
Available-for-sale Securities, Gross Unrealized Gain	5,385	5,837
Available-for-sale Securities, Gross Unrealized Loss	(751)	(1,106)
Securities available‑for‑sale	149,569	144,796
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	1,449,194	1,508,968
Available-for-sale Securities, Gross Unrealized Gain	104,093	39,435
Available-for-sale Securities, Gross Unrealized Loss	(1)	(1,072)
Securities available‑for‑sale	1,553,286	1,547,331
Government agency and government-sponsored enterprise commercial mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	449,096	392,729
Available-for-sale Securities, Gross Unrealized Gain	15,584	1,509
Available-for-sale Securities, Gross Unrealized Loss	(281)	(2,797)
Securities available‑for‑sale	464,399	391,441
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	47,218	49,047
Available-for-sale Securities, Gross Unrealized Gain	935	327
Available-for-sale Securities, Gross Unrealized Loss	(1,426)	(950)
Securities available‑for‑sale	46,727	48,424
Collateralized loan obligations
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	155,309	133,192
Available-for-sale Securities, Gross Unrealized Gain	376	128
Available-for-sale Securities, Gross Unrealized Loss	(1,798)	(1,131)
Securities available‑for‑sale	153,887	132,189
SBA securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	195,621	211,946
Available-for-sale Securities, Gross Unrealized Gain	1,977	41
Available-for-sale Securities, Gross Unrealized Loss	(297)	(830)
Securities available‑for‑sale	197,301	211,157
US Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	0	70,196
Available-for-sale Securities, Gross Unrealized Gain	0	0
Available-for-sale Securities, Gross Unrealized Loss	0	(816)
Securities available‑for‑sale	0	69,380
US Government-sponsored Enterprises Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	0	36,302
Available-for-sale Securities, Gross Unrealized Gain	0	611
Available-for-sale Securities, Gross Unrealized Loss	0	0
Securities available‑for‑sale	0	36,913
Asset-backed and other securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	96,910	116,723
Available-for-sale Securities, Gross Unrealized Gain	439	119
Available-for-sale Securities, Gross Unrealized Loss	(702)	(1,631)
Securities available‑for‑sale	$ 96,647	$ 115,211

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=51813488&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=27724398&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=49167202&loc=d3e26610-111562

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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