BUSINESS ACQUISITION - Pro forma information of acquisitions in 2017 and 2018 - (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019	Jan. 31, 2019
BUSINESS ACQUISITION
Initial public offering price		$ 10.00
Gain of fair value change of contingent consideration	$ 65,594

This element represents the amount of any change recognized during the period in the high-end of the estimated range of outcomes (undiscounted) of a liability assumed in a business combination arising from an item of contingent consideration.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e7008-128479

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration