Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Contract Liabilities (Details)

v3.20.1
Summary of Significant Accounting Policies - Contract Liabilities (Details)
3 Months Ended
Mar. 31, 2019
USD ($)
Summary of Significant Accounting Policies  
Amounts included in contract liability at the beginning of the period $ 2,686,000