Investment Securities (Details 1) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	$ 3,219,600	$ 3,512,385
Available-for-sale Securities, Gross Unrealized Gain	125,080	62,157
Available-for-sale Securities, Gross Unrealized Loss	(3,345)	(15,105)
Securities available‑for‑sale	3,341,335	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	518,996	660,069
Available-for-sale Securities, Gross Unrealized Gain	10,639	11,517
Available-for-sale Securities, Gross Unrealized Loss	(694)	(3,746)
Securities available‑for‑sale	528,941	667,840
Government agency and government-sponsored enterprise collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	154,216	193,148
Available-for-sale Securities, Gross Unrealized Gain	3,196	2,633
Available-for-sale Securities, Gross Unrealized Loss	(181)	(1,026)
Securities available‑for‑sale	157,231	194,755
Private label collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	133,917	140,065
Available-for-sale Securities, Gross Unrealized Gain	5,377	5,837
Available-for-sale Securities, Gross Unrealized Loss	(669)	(1,106)
Securities available‑for‑sale	138,625	144,796
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	1,437,952	1,508,968
Available-for-sale Securities, Gross Unrealized Gain	84,571	39,435
Available-for-sale Securities, Gross Unrealized Loss	(29)	(1,072)
Securities available‑for‑sale	1,522,494	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	517,163	392,729
Available-for-sale Securities, Gross Unrealized Gain	15,299	1,509
Available-for-sale Securities, Gross Unrealized Loss	(1,189)	(2,797)
Securities available‑for‑sale	531,273	391,441
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	47,155	49,047
Available-for-sale Securities, Gross Unrealized Gain	1,856	327
Available-for-sale Securities, Gross Unrealized Loss	0	(950)
Securities available‑for‑sale	49,011	48,424
Collateralized loan obligations
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	155,373	133,192
Available-for-sale Securities, Gross Unrealized Gain	1,511	128
Available-for-sale Securities, Gross Unrealized Loss	(237)	(1,131)
Securities available‑for‑sale	156,647	132,189
SBA securities
Schedule of Available-for-sale Securities [Line Items]
Total securities available-for-sale	185,639	211,946
Available-for-sale Securities, Gross Unrealized Gain	1,909	41
Available-for-sale Securities, Gross Unrealized Loss	(248)	(830)
Securities available‑for‑sale	187,300	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	69,189	116,723
Available-for-sale Securities, Gross Unrealized Gain	722	119
Available-for-sale Securities, Gross Unrealized Loss	(98)	(1,631)
Securities available‑for‑sale	$ 69,813	$ 115,211