Investment Securities (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ (1,026,780)	$ (1,366,218)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(223,832)	(264,479)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(1,250,612)	(1,630,697)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(8,928)	(19,706)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(7,131)	(2,505)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(16,059)	(22,211)
Government agency and government-sponsored enterprise pass through securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(44,795)	(149,281)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(26,010)	(122,902)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(70,805)	(272,183)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(311)	(1,691)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(533)	(1,273)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(844)	(2,964)
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(163,014)	(44,111)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(20,928)	(25,316)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(183,942)	(69,427)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,452)	(416)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(445)	(81)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2,897)	(497)
Private Label Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(50,521)	(49,067)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(5,035)	(30,155)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(55,556)	(79,222)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(500)	(906)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(142)	(531)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(642)	(1,437)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(67,936)	(644,424)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(32,326)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(100,262)	(644,424)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(365)	(6,011)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(974)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,339)	(6,011)
Commercial Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(579,373)	(349,550)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(129,060)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(708,433)	(349,550)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,777)	(9,658)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4,981)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(8,758)	(9,658)
Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		(29,829)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		(29,829)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(271)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(271)
Collateralized Loan Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		(12,450)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		(39,231)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		(51,681)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(37)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		(201)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(238)
SBA asset-backed securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(74,904)	(69,293)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	(39,024)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(74,904)	(108,317)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(575)	(407)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(343)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(575)	(750)
Other securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(46,237)	(18,213)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(10,473)	(7,851)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(56,710)	(26,064)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(948)	(309)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(56)	(76)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (1,004)	$ (385)