DISCONTINUED OPERATIONS - Condensed cash flows (Details) - Discontinued business - 2C intra-regional business and loan-facilitation related service ¥ in Thousands	12 Months Ended
Dec. 31, 2019 CNY (¥)
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Net cash used in operating activities	¥ (821,185)
Net cash used in investing activities	¥ (187)

Amount of cash inflow (outflow) of investing activities of discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3521-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760

Name:	us-gaap_CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration