Summary of Significant Accounting Policies - Recent accounting pronouncements (Details) - ASU 2016-01 - USD ($)	Dec. 31, 2018	Jan. 01, 2018
Accumulated Other Comprehensive Loss
Recent accounting pronouncements
Reclassification on adoption of ASU 2016-01	$ (73,000)
Accumulated Deficit
Recent accounting pronouncements
Reclassification on adoption of ASU 2016-01	$ 73,000
Adjustment | Accumulated Other Comprehensive Loss
Recent accounting pronouncements
Reclassification on adoption of ASU 2016-01		$ (73,000)
Adjustment | Accumulated Deficit
Recent accounting pronouncements
Reclassification on adoption of ASU 2016-01		$ 73,000