PRINCIPAL ACCOUNTING POLICIES (Cash, cash equivalents and restricted cash) (Details)	Dec. 31, 2020 CNY (¥)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 CNY (¥)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 CNY (¥)	Dec. 31, 2017 CNY (¥)
PRINCIPAL ACCOUNTING POLICIES
Cash and cash equivalent	¥ 7,481,678,114	$ 1,146,617,335	¥ 5,653,853,691
Restricted cash	593,093,671	90,895,582	576,546,098
Cash and cash equivalents included in held-for-sale assets			43,558,640
Total	¥ 8,074,771,785	$ 1,237,512,917	¥ 6,273,958,429	$ 961,526,196	¥ 3,482,027,573	¥ 2,761,374,804

Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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