Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases
Operating lease ROU assets	$ 1,849
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Operating lease ROU assets
Operating lease liabilities	$ 1,892
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Operating lease liabilities
Operating lease weighted average discount rate	1.04%
Lessee, Operating Lease, Existence of Option to Extend [true/false]	true
Operating lease renewal term (in years)	5 years
Operating lease weighted average remaining lease term		5 years
Operating lease rent expense	$ 98	$ 105
Minimum
Leases
Operating lease remaining term	11 months
Maximum
Leases
Operating lease remaining term	6 years