SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Finite-Lived Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill from business combinations
Goodwill	$ 25,111,000	$ 25,111,000
Goodwill impairment charges	0	0	$ 0
Finite-Lived Intangible Assets
Net intangible asset balance	$ 1,538,000	$ 2,704,000