FAIR VALUE MEASUREMENTS - Contingent consideration (Details) $ in Thousands	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Minimum | Valuation Technique, Forecasted Growth Rates
Inputs used in the fair value measurement of estimated contingent consideration
Estimated contingent consideration (in percent)	(32.1)	(10.7)
Minimum | Valuation Technique, Discount Rates
Inputs used in the fair value measurement of estimated contingent consideration
Estimated contingent consideration (in percent)	8
Maximum | Valuation Technique, Forecasted Growth Rates
Inputs used in the fair value measurement of estimated contingent consideration
Estimated contingent consideration (in percent)	26.6	51.1
Maximum | Valuation Technique, Discount Rates
Inputs used in the fair value measurement of estimated contingent consideration
Estimated contingent consideration (in percent)	20
Level 3
Inputs used in the fair value measurement of estimated contingent consideration
Estimated contingent consideration	$ 124,217	$ 183,568
Valuation techniques	us-gaap:ValuationTechniqueOptionPricingModelMember	us-gaap:ValuationTechniqueOptionPricingModelMember
Unobservable input	focs:MeasurementInputForecastedGrowthRatesMember	focs:MeasurementInputForecastedGrowthRatesMember
Level 3 | Minimum | Valuation Technique, Discount Rates
Inputs used in the fair value measurement of estimated contingent consideration
Estimated contingent consideration (in percent)		11
Level 3 | Maximum | Valuation Technique, Discount Rates
Inputs used in the fair value measurement of estimated contingent consideration
Estimated contingent consideration (in percent)		17