Investment Securities (Details 2) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 391,063	$ 106,602
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(5,494)	(882)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	44,605	173,724
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(1,093)	(2,720)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	435,668	280,326
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(6,587)	(3,602)
Government agency and government-sponsored enterprise pass through securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	17,968	10,711
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(95)	(13)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	9,552	27,100
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(101)	(359)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	27,520	37,811
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(196)	(372)
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	23,908
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	(73)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	14,444	40,652
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(421)	(1,007)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	14,444	64,560
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(421)	(1,080)
Covered private label collateralized mortgage obligation [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,111	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(44)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	589	1,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(66)	(95)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,700	1,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(110)	(95)
Other Private Label Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,296	1,618
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(2)	(93)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,099	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(38)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,395	1,618
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(40)	(93)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	238,631	11,854
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(3,988)	(66)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	529	84,822
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(14)	(1,216)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	239,160	96,676
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(4,002)	(1,282)
Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	23,013	52,071
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(105)	(547)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,278	10,131
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(18)	(15)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	25,291	62,202
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(123)	(562)
Collateralized Loan Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	103,409
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(1,158)
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, Aggregate Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	103,409
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(1,158)
Other securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,635	6,440
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(102)	(90)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	16,114	10,019
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(435)	(28)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	21,749	16,459
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	$ (537)	$ (118)