Fair Value - Financial Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	$ 404,825	$ 459,043
I/O strip receivables	503	568
Agency mortgage-backed securities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	284,361	302,854
U.S. Treasury
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	120,464	148,753
U.S. Government sponsored entities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale		7,436
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	120,464	148,753
Significant Other Observable Inputs (Level 2)
Financial Assets and Liabilities Measured on a Recurring Basis
I/O strip receivables	503	568
Significant Other Observable Inputs (Level 2) | Agency mortgage-backed securities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale	284,361	302,854
Significant Other Observable Inputs (Level 2) | U.S. Government sponsored entities
Financial Assets and Liabilities Measured on a Recurring Basis
Securities available-for-sale		7,436
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