Significant Accounting Policies - Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash		$ 20	$ 10
ASU 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash		$ 20	$ 10
Scenario, Forecast | ASU 2016-02 | Subsequent Event | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use asset	$ 100
Lease, liability	100
Scenario, Forecast | ASU 2016-02 | Subsequent Event | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use asset	400
Lease, liability	$ 400