Commitments and Contingencies Commitments and Contingencies - Hedged Assets Related to Interest Rate Derivatives (Details) - Derivatives designated as hedging instruments - Interest rate swaps - Fair value hedge - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Carrying Amount of the Hedged Asset	$ 7,882	$ 8,412
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Asset	$ 346	$ 637