FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of contingent consideration liabilities, net	$ (13.6)	$ 6.1	$ 5.7
Measurement Input, Discount Rate | Minimum | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.0008
Measurement Input, Discount Rate | Maximum | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.0853
Measurement Input, Discount Rate | Weighted Average | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.031
Measurement Input, Probability of Milestone Achievement | Minimum | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.004
Measurement Input, Probability of Milestone Achievement | Maximum | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.997
Measurement Input, Probability of Milestone Achievement | Weighted Average | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.707
Measurement Input, Volatility of Future Revenue | Minimum | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.370
Measurement Input, Volatility of Future Revenue | Maximum | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.400
Measurement Input, Volatility of Future Revenue | Weighted Average | Level 3 | Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration liability measurement input	0.388
Two Previous Acquisitions
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of contingent consideration liabilities, net	$ 12.7	$ 24.1