Securities - Carrying Value (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost
One to five years	$ 1,206
Five to ten years	36,703
After ten years	225,374
Amortized Cost	263,283
Amortized cost	500,543	$ 471,070
Held-to-maturity securities, Five to ten years	12,444
Held-to-maturity securities, After ten years	6,768
Held-to-maturity securities, Amortized Cost	19,212
Fair Value
One to five years	1,182
Five to ten years	36,027
After ten years	222,729
Fair Value	259,938
Fair Value	492,468	456,700
Held-to-maturity securities, Five to ten years	12,513
Held-to-maturity securities, After ten years	6,558
Held-to-maturity securities, Fair Value	19,071
Mortgage-backed securities
Amortized Cost
Amortized cost	224,311	238,354
Fair Value
Fair Value	219,579	231,641
Asset-backed securities
Amortized Cost
Amortized cost	9,949	19,470
Fair Value
Fair Value	10,000	19,534
Other securities
Amortized Cost
Amortized cost	3,000	3,000
Fair Value
Fair Value	$ 2,951	$ 2,932