Investment Securities (Details 1) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	$ 2,196,523	$ 1,026,780
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(48,298)	(8,928)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	645,464	223,832
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(30,168)	(7,131)
Unrealized Losses on Securities Available-for-Sale, Fair Value	2,841,987	1,250,612
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(78,466)	(16,059)
Government agency and government-sponsored enterprise pass through securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	76,238	44,795
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(1,332)	(311)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	51,861	26,010
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(1,958)	(533)
Unrealized Losses on Securities Available-for-Sale, Fair Value	128,099	70,805
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(3,290)	(844)
Government agency and government-sponsored enterprise collateralized mortgage obligations
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	401,795	163,014
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(6,418)	(2,452)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	140,997	20,928
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(7,259)	(445)
Unrealized Losses on Securities Available-for-Sale, Fair Value	542,792	183,942
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(13,677)	(2,897)
Private label collateralized mortgage obligations
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	46,713	50,521
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(1,101)	(500)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	34,654	5,035
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(1,501)	(142)
Unrealized Losses on Securities Available-for-Sale, Fair Value	81,367	55,556
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(2,602)	(642)
Municipal securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	436,012	67,936
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(8,743)	(365)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	55,402	32,326
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(3,149)	(974)
Unrealized Losses on Securities Available-for-Sale, Fair Value	491,414	100,262
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(11,892)	(1,339)
Government agency and government-sponsored enterprise commercial mortgage-backed securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	784,452	579,373
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(26,454)	(3,777)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	292,553	129,060
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(14,290)	(4,981)
Unrealized Losses on Securities Available-for-Sale, Fair Value	1,077,005	708,433
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(40,744)	(8,758)
US Treasury Securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	397,631
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(2,960)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	397,631
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(2,960)
SBA asset-backed securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	32,867	74,904
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(1,143)	(575)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	34,719	0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(1,270)	0
Unrealized Losses on Securities Available-for-Sale, Fair Value	67,586	74,904
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(2,413)	(575)
Asset-backed
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	20,815	45,198
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(147)	(818)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	35,278	10,473
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(741)	(56)
Unrealized Losses on Securities Available-for-Sale, Fair Value	56,093	55,671
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	$ (888)	(874)
Equity Securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value		1,039
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses		(130)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value		0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses		0
Unrealized Losses on Securities Available-for-Sale, Fair Value		1,039
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses		$ (130)