Quarterly report pursuant to Section 13 or 15(d)

Revenue Recognition - Changes in Contractual Liabilities Balance (Details)

v3.21.1
Revenue Recognition - Changes in Contractual Liabilities Balance (Details) - USD ($)
3 Months Ended 42 Months Ended
Mar. 31, 2021
Mar. 31, 2021
Contract with Customer, Liability [Abstract]    
Beginning balance $ 16,378,000  
Revenue recognized 790,000 $ 0
Ending balance $ 15,588,000 $ 15,588,000