FAIR VALUE MEASUREMENTS (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2020 CNY (¥)	Dec. 31, 2019 CNY (¥)	Dec. 31, 2018 CNY (¥)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest income	$ 10,053	¥ 65,596	¥ 84,276	¥ 53,111
Recurring \| Level 2 \| Wealth management products
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		470,000	242,567
Interest income		¥ 7,855	¥ 6,928	¥ 12,263

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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