FAIR VALUE - Contingent Consideration Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Oct. 31, 2019	May 31, 2019
Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration obligation	$ 31,140	$ 5,930
Fusion Acquisition | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration obligation	26,910	0
Noble Acquisition
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration obligation	4,200		$ 2,900
Noble Acquisition | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration obligation	4,230	2,930
Gateway Acquisition
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration obligation				$ 3,000
Gateway Acquisition | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration obligation	$ 0	$ 3,000