SHARE INCENTIVE PLANS - Stock option plans (Details) - shares	Jul. 25, 2019	Jul. 25, 2018	Feb. 14, 2017	Dec. 31, 2019	Mar. 14, 2016
Share-based compensation
Total shares reserved for future issuance (in shares)				8,468,966	0
All other stock option plans
Share-based compensation
Total shares reserved for future issuance (in shares)					750,000
Second Restated Plan
Share-based compensation
Total shares reserved for future issuance (in shares)			2,390,000
Number of shares reserved for future issuance, increase (decease)			1,640,000
Third Restated Plan
Share-based compensation
Total shares reserved for future issuance (in shares)		4,467,000
Number of shares reserved for future issuance, increase (decease)		2,077,000
Fourth Restated Plan
Share-based compensation
Total shares reserved for future issuance (in shares)	6,427,000
Number of shares reserved for future issuance, increase (decease)	1,960,000