ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair value measurements on recurring and nonrecurring valuation techniques (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Contingent Consideration [Member] | Measurement Input, Price Volatility [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions Measurement Rate	23.00%	34.60%
Contingent Consideration [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions Measurement Rate	14.50%	15.00%
Employment Agreement Award [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions Measurement Rate	11.00%	11.00%
Employment Agreement Award [Member] | Measurement Input, Long-term Revenue Growth Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions Measurement Rate	2.50%	2.50%
Redeemable Noncontrolling Interest [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions Measurement Rate	10.50%	10.50%
Redeemable Noncontrolling Interest [Member] | Measurement Input, Long-term Revenue Growth Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions Measurement Rate	1.00%	1.00%