SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of Credit Risk (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Concentration of Credit Risk
Cash and cash equivalents, federal government agency insured limit	$ 125.7
Revenue | Customer Concentration Risk | Centers for Medicare and Medicaid Services
Concentration of Credit Risk
Concentration risk (as a percent)	14.00%	20.00%	21.00%
Revenue | Customer Concentration Risk | UnitedHealthcare
Concentration of Credit Risk
Concentration risk (as a percent)	12.00%	11.00%	10.00%
Revenue | Customer Concentration Risk | State of Wisconsin
Concentration of Credit Risk
Concentration risk (as a percent)	3.00%	8.00%	12.00%
Accounts Receivable | Customer Concentration Risk | Centers for Medicare and Medicaid Services
Concentration of Credit Risk
Concentration risk (as a percent)	14.00%	11.00%	14.00%
Accounts Receivable | Customer Concentration Risk | UnitedHealthcare
Concentration of Credit Risk
Concentration risk (as a percent)	9.00%	8.00%	7.00%
Accounts Receivable | Customer Concentration Risk | State of Wisconsin
Concentration of Credit Risk
Concentration risk (as a percent)	5.00%	9.00%	22.00%