Investments (Details 2) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 223,023	$ 773,925
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(1,346)	(33,356)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	227,887	5,032
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(5,399)	(189)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	450,910	778,957
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(6,745)	(33,545)
Government agency and government-sponsored enterprise pass through securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	38,316	148,662
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(191)	(2,767)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	27,894	32
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(608)	(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	66,210	148,694
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(799)	(2,768)
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	159,329	179,938
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(967)	(4,486)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	42,340	4,383
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(1,518)	(98)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	201,669	184,321
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(2,485)	(4,584)
Covered private label collateralized mortgage obligation [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	1,640
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	(60)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	1,050	617
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(89)	(90)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	1,050	2,257
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(89)	(150)
Other Private Label Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	893
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(5)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	893
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(5)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	18,058	337,208
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(75)	(24,273)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	133,602
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(3,136)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	151,660	337,208
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(3,211)	(24,273)
Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	72,636
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	(1,483)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	12,971	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(28)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	12,971	72,636
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	(28)	(1,483)
US Government-sponsored Enterprises Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	9,872
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	(174)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	0	9,872
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0	(174)
Other securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	6,427	23,969
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	(108)	(113)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	10,030	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	(20)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	16,457	23,969
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ (128)	$ (113)