Investments Investment Securities in Unrealized Loss Position (Details) $ in Thousands		Jun. 30, 2017 USD ($) securities	Dec. 31, 2016 USD ($) securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 653,877	$ 818,909
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		(13,795)	(22,042)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		47,678	44,907
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		(1,604)	(1,622)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		701,555	863,816
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 15,399	$ 23,664
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities		171	230
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 81,333	$ 87,483
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(386)	(476)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value		81,333	87,483
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ (386)	$ (476)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities		17	15
US Government and Government Agencies and Authorities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 24,367	$ 19,094
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		(587)	(838)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		292	643
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		(6)	(16)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		24,659	19,737
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 593	$ 854
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities		4	4
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 14,971
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(4)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value		14,971
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ (4)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities		4
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 97,093	$ 125,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		(1,185)	(2,259)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		97,093	125,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 1,185	$ 2,259
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities		15	18
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 74,816	$ 182,395
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		(2,144)	(4,957)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		2,020	2,720
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		(43)	(33)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		76,836	185,115
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 2,187	$ 4,990
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities		47	109
Mortgage Backed Securities, Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	[1]	$ 457,585	$ 492,008
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	[1]	(9,874)	(13,988)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	[1]	45,366	41,544
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	[1]	(1,555)	(1,573)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	[1]	502,951	533,552
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	[1]	$ 11,429	$ 15,561
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities	[1]	103	99
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	[1]	$ 66,362	$ 87,483
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	[1]	(382)	(476)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	[1]	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	[1]	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	[1]	66,362	87,483
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	$ (382)	$ (476)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities	[1]	13	15
Other Aggregated Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 16	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		(5)	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, 12 Months or Longer, Aggregate Losses		0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		16	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 5	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities		2	0

[1] All mortgage-backed securities are guaranteed by U.S. government agencies or government-sponsored entities.