Fair Value - Financial Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	$ 335,923	$ 391,852
I/O strip receivables	919	968
Agency mortgage-backed securities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	328,505	374,733
Trust preferred securities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale		17,119
U.S. Government sponsored entities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	7,418
Significant Other Observable Inputs (Level 2)
Financial Assets and Liabilities Measured on a Recurring Basis
I/O strip receivables	919	968
Significant Other Observable Inputs (Level 2) | Agency mortgage-backed securities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	328,505	374,733
Significant Other Observable Inputs (Level 2) | Trust preferred securities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale		17,119
Significant Other Observable Inputs (Level 2) | U.S. Government sponsored entities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	7,418
Recurring basis
Transfers between Level 1 and Level 2
Transfers between Level 1 and Level 2	0	0
Transfers between Level 2 and Level 1	$ 0	$ 0