Investments (Details 1) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ (1,377,664)	$ (106,602)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(41,832)	(173,724)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,473)	(2,720)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(13,632)	(882)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(15,105)	(3,602)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(1,419,496)	(280,326)
Government agency and government-sponsored enterprise pass through securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(391,642)	(10,711)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(9,342)	(27,100)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(266)	(359)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,893)	(13)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(4,159)	(372)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(400,984)	(37,811)
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(314,284)	(23,908)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(14,230)	(40,652)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(641)	(1,007)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,769)	(73)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,410)	(1,080)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(328,514)	(64,560)
Covered Private Label Collateralized Mortgage Obligation [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(1,354)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(568)	(1,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(68)	(95)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(57)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(125)	(95)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(1,922)	(1,000)
Other Private Label Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(92,179)	(1,618)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(1,070)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(38)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(943)	(93)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(981)	(93)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(93,249)	(1,618)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(126,892)	(11,854)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(531)	(84,822)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(11)	(1,216)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,061)	(66)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,072)	(1,282)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(127,423)	(96,676)
US Treasury Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(69,380)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(816)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(816)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(69,380)
Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(29,379)	(52,071)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	(10,131)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(15)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(950)	(547)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(950)	(562)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(29,379)	(62,202)
Collateralized Loan Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(100,993)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,131)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,131)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(100,993)
Asset-backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(179,942)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(830)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(830)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(179,942)
Other securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(71,619)	(6,440)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(16,091)	(10,019)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(449)	(28)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,182)	(90)
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,631)	(118)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ (87,710)	$ (16,459)