Investments - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available for sale, Amortized Cost
Due in one year or less	$ 3,199
Due after one year through five years	121,522
Due after five years through ten years	11,141
Due after ten years	3,537
Mortgage-backed securities	311,516
Amortized Cost	450,915	$ 396,782
Available for sale, Estimated Fair Value
Due in one year or less	3,225
Due after one year through five years	122,673
Due after five years through ten years	11,543
Due after ten years	3,268
Mortgage-backed securities	311,061
Securities available for sale	451,770	400,146
Held to maturity, Amortized Cost
Due in one year or less	0
Due after one year through five years	4,641
Due after five years through ten years	10,190
Due after ten years	0
Mortgage-backed securities	28,883
Amortized Cost	43,714	45,985
Held to maturity, Estimated Fair Value
Due in one year or less	0
Due after one year through five years	4,662
Due after five years through ten years	10,182
Due after ten years	0
Mortgage-backed securities	28,597
Held to maturity, fair value	$ 43,441	$ 45,795