ACQUISITIONS - Hotels and Companies (Details) - Series of Individually Immaterial Business Acquisitions [Member] ¥ in Millions	12 Months Ended
Dec. 31, 2020 CNY (¥) item	Dec. 31, 2019 CNY (¥) item	Dec. 31, 2018 CNY (¥) item
Acquisitions
Cash consideration \| ¥	¥ 26	¥ 54	¥ 7
Number of hotels acquired			2
Number of companies acquired	3	3

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585

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