PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Statement of Comprehensive Loss (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($)	Dec. 31, 2019 CNY (¥)	Dec. 31, 2018 CNY (¥)	Dec. 31, 2017 CNY (¥)
Condensed statements of comprehensive loss
Net loss	$ (26,183)	¥ (182,292)	¥ (205,065)	¥ (772,730)
Other comprehensive (loss) income, net of tax of nil:
Comprehensive loss	(27,193)	(189,321)	(98,084)	(1,038,607)
Comprehensive loss attributable to the Company's ordinary shareholders	(27,343)	(190,367)	(116,413)	(893,693)
Parent Company
Condensed statements of comprehensive loss
Net loss	(26,183)	(182,292)	(205,065)	(772,730)
Other comprehensive (loss) income, net of tax of nil:
Foreign currency translation adjustments, net of tax of nil	(1,160)	(8,075)	88,652	(120,963)
Other comprehensive (loss) income, net of tax of nil:	(1,160)	(8,075)	88,652	(120,963)
Comprehensive loss	(27,343)	(190,367)	(116,413)	(893,693)
Comprehensive loss attributable to the Company's ordinary shareholders	$ (27,343)	¥ (190,367)	¥ (116,413)	¥ (893,693)

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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