CASH AND CASH EQUIVALENTS AND SHORT-TERM DEPOSITS (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020 CNY (¥)	Dec. 31, 2020 USD ($)	[1]	Dec. 31, 2019 CNY (¥)	Dec. 31, 2019 USD ($)	[1]	Dec. 31, 2018 CNY (¥)	Dec. 31, 2017 CNY (¥)
CASH AND CASH EQUIVALENTS [abstract]
Cash at bank and on hand	¥ 1,485,232			¥ 1,562,334
Term deposits with initial term not more than three months	0			0
Cash and cash equivalents	¥ 1,485,232	$ 227,622		¥ 1,562,334	$ 239,438		¥ 1,738,753	¥ 1,160,515

[1] Translation of amounts from Renminbi ("RMB") into United States dollars ("US$") for the convenience of the reader has been made at US$1.00=RMB6.5250, the certified exchange rates for December 31, 2020 as published by the Federal Reserve Board of the United States. No representation is made that the RMB amounts could have been, or could be, converted into US$ at that rate on December 31, 2020 or on any other date.