Securities, Available-for-sale (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	$ 118,914	$ 450,662
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	1,215	5,344
Investments with an Unrealized Loss of 12 months or longer, Fair Value	79,169	178,215
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	1,752	3,989
Total Investments with an Unrealized Loss, Fair Value	198,083	628,877
Total Investments with an Unrealized Loss, Unrealized Losses	2,967	9,333
US Treasury Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	0	0
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	0	0
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	0	0
Total Investments with an Unrealized Loss, Unrealized Losses	0	0
U.S. Government Agency Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	8,841	61,903
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	509	1,702
Investments with an Unrealized Loss of 12 months or longer, Fair Value	12,116	65,538
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	571	1,607
Total Investments with an Unrealized Loss, Fair Value	20,957	127,441
Total Investments with an Unrealized Loss, Unrealized Losses	1,080	3,309
Mortgage-backed Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	67,682	338,230
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	279	2,789
Investments with an Unrealized Loss of 12 months or longer, Fair Value	41,087	103,003
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	527	2,241
Total Investments with an Unrealized Loss, Fair Value	108,769	441,233
Total Investments with an Unrealized Loss, Unrealized Losses	806	5,030
State and Municipal Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	2,607	6,509
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	12	38
Investments with an Unrealized Loss of 12 months or longer, Fair Value	412	6,135
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	1	134
Total Investments with an Unrealized Loss, Fair Value	3,019	12,644
Total Investments with an Unrealized Loss, Unrealized Losses	13	172
Asset-backed Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	38,787	41,466
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	409	798
Investments with an Unrealized Loss of 12 months or longer, Fair Value	25,554	3,539
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	653	7
Total Investments with an Unrealized Loss, Fair Value	64,341	45,005
Total Investments with an Unrealized Loss, Unrealized Losses	1,062	805
Corporate Notes [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	997	2,554
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	6	17
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	997	2,554
Total Investments with an Unrealized Loss, Unrealized Losses	$ 6	$ 17