Basis of Financial Statement Presentation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2017	Jan. 01, 2019
Basis of Financial Statement Presentation
Election of practical expedients package	true
Operating lease, ROU asset	$ 1,100
Operating lease, ROU asset, Statement of Financial Position	us-gaap:PropertyPlantAndEquipmentNet
Operating lease liability	$ 1,124
Operating lease, liability, Statement of Financial Position	us-gaap:AccruedLiabilitiesAndOtherLiabilities
ASU 2016-02 | Adjustment
Basis of Financial Statement Presentation
Operating lease, ROU asset			$ 1,200
Operating lease, ROU asset, Statement of Financial Position			us-gaap:PropertyPlantAndEquipmentNet
Operating lease liability			$ 1,200
Operating lease, liability, Statement of Financial Position			us-gaap:AccruedLiabilitiesAndOtherLiabilities
ASU 2018-02
Basis of Financial Statement Presentation
Reclassification from accumulated other comprehensive loss to retained earnings		$ 66