Annual report pursuant to Section 13 and 15(d)

COMMITMENTS AND CONTINGENCIES - Expense charged to operations under the operating lease agreements (Details)

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COMMITMENTS AND CONTINGENCIES - Expense charged to operations under the operating lease agreements (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
COMMITMENTS AND CONTINGENCIES      
Rent expense $ 6,294,000 $ 5,597,000 $ 4,299,000