Post-effective amendment to a registration statement that is not immediately effective upon filing

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Maintenance and Repair Costs (Details)

v3.21.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Maintenance and Repair Costs (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2018
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES    
Maintenance and repair cost   $ 4,276,000
Amortization period 18 months  
Amortization period of deferred maintenance cost   $ 3,753,000