FAIR VALUE MEASUREMENTS - Schedule of fair value measurement valuation (Details)	Mar. 31, 2020 USD ($)	Oct. 31, 2018 USD ($)	Jun. 11, 2018 USD ($)	Jun. 14, 2017 USD ($)
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration		$ 0	$ 0	$ 0
Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration		$ 46,800,000	$ 4,400,000	$ 1,000,000.0
Fair Value | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 22,342,000
Option pricing model | Level 3 | Customer growth rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.007
Option pricing model | Minimum | Level 3 | Operating results growth rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.087
Option pricing model | Minimum | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.103
Option pricing model | Maximum | Level 3 | Operating results growth rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.371
Option pricing model | Maximum | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.105
Option pricing model | Weighted average | Level 3 | Operating results growth rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.229
Option pricing model | Weighted average | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.104
Scenario approach based on interest rate forecasts | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0