MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($)	Dec. 31, 2019 CNY (¥)	Dec. 31, 2018 CNY (¥)	Dec. 31, 2017 CNY (¥)
PRC
MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN
Total expense for defined contribution plan	$ 17,419	¥ 121,266	¥ 122,362	¥ 134,053

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