Securities - AFS in an Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($) item
Number of Securities
Unrealized loss for less than twelve months | item	41	17
Unrealized loss for twelve months or longer | item	49	117
Total | item	90	134
Fair Value
Unrealized loss for less than twelve months	$ 217,328	$ 54,123
Unrealized loss for twelve months or longer	116,001	503,022
Estimated Fair Value, Total	333,329	557,145
Unrealized Loss
Unrealized loss for less than twelve months	2,135	227
Unrealized loss for twelve months or longer	3,181	10,535
Total	$ 5,316	$ 10,762
U.S. Treasury securities
Number of Securities
Unrealized loss for less than twelve months | item	8	4
Unrealized loss for twelve months or longer | item		1
Total | item	8	5
Fair Value
Unrealized loss for less than twelve months	$ 33,791	$ 7,703
Unrealized loss for twelve months or longer		1,706
Estimated Fair Value, Total	33,791	9,409
Unrealized Loss
Unrealized loss for less than twelve months	33	27
Unrealized loss for twelve months or longer		6
Total	$ 33	$ 33
Bonds
Number of Securities
Unrealized loss for less than twelve months | item	7	3
Unrealized loss for twelve months or longer | item	3	22
Total | item	10	25
Fair Value
Unrealized loss for less than twelve months	$ 148,327	$ 34,847
Unrealized loss for twelve months or longer	44,321	373,035
Estimated Fair Value, Total	192,648	407,882
Unrealized Loss
Unrealized loss for less than twelve months	896	153
Unrealized loss for twelve months or longer	1,051	7,363
Total	$ 1,947	$ 7,516
Residential mortgage-backed securities
Number of Securities
Unrealized loss for less than twelve months | item	3
Unrealized loss for twelve months or longer | item	1
Total | item	4
Fair Value
Unrealized loss for less than twelve months	$ 3,407
Unrealized loss for twelve months or longer	982
Estimated Fair Value, Total	4,389
Unrealized Loss
Unrealized loss for less than twelve months	5
Unrealized loss for twelve months or longer	14
Total	$ 19
Commercial mortgage-backed securities
Number of Securities
Unrealized loss for less than twelve months | item	1
Unrealized loss for twelve months or longer | item		4
Total | item	1	4
Fair Value
Unrealized loss for less than twelve months	$ 1,611
Unrealized loss for twelve months or longer		$ 11,056
Estimated Fair Value, Total	1,611	11,056
Unrealized Loss
Unrealized loss for less than twelve months	2
Unrealized loss for twelve months or longer		137
Total	$ 2	$ 137
Collateralized mortgage obligations
Number of Securities
Unrealized loss for less than twelve months | item	2	3
Unrealized loss for twelve months or longer | item	8	8
Total | item	10	11
Fair Value
Unrealized loss for less than twelve months	$ 1,590	$ 7,141
Unrealized loss for twelve months or longer	42,399	61,108
Estimated Fair Value, Total	43,989	68,249
Unrealized Loss
Unrealized loss for less than twelve months	4	40
Unrealized loss for twelve months or longer	1,640	2,260
Total	$ 1,644	$ 2,300
Corporate securities
Number of Securities
Unrealized loss for less than twelve months | item	16
Unrealized loss for twelve months or longer | item	1	1
Total | item	17	1
Fair Value
Unrealized loss for less than twelve months	$ 16,635
Unrealized loss for twelve months or longer	1,949	$ 1,939
Estimated Fair Value, Total	18,584	1,939
Unrealized Loss
Unrealized loss for less than twelve months	277
Unrealized loss for twelve months or longer	49	59
Total	$ 326	$ 59
States and political subdivisions
Number of Securities
Unrealized loss for less than twelve months | item	2	7
Unrealized loss for twelve months or longer | item	35	81
Total | item	37	88
Fair Value
Unrealized loss for less than twelve months	$ 3,018	$ 4,432
Unrealized loss for twelve months or longer	24,423	54,178
Estimated Fair Value, Total	27,441	58,610
Unrealized Loss
Unrealized loss for less than twelve months	9	7
Unrealized loss for twelve months or longer	93	710
Total	$ 102	$ 717
Equity securities
Number of Securities
Unrealized loss for less than twelve months | item	2
Unrealized loss for twelve months or longer | item	1
Total | item	3
Fair Value
Unrealized loss for less than twelve months	$ 8,949
Unrealized loss for twelve months or longer	1,927
Estimated Fair Value, Total	10,876
Unrealized Loss
Unrealized loss for less than twelve months	909
Unrealized loss for twelve months or longer	334
Total	$ 1,243