Fair Values of Financial Instruments - Reconciliation of Beginning and Ending Balances of Recurring Fair Value Measurements using Significant Unobservable Level 3 Inputs (Details) - Fair Value, Measurements, Recurring - Available for Sale Securities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Available for Sale Securities
Beginning Balance	$ 3,978	$ 5,169
Included in other comprehensive income	(49)	26
Principal payments	(601)	(1,217)
Ending balance	$ 3,328	$ 3,978