Summary of significant accounting policies - Loan receivables from Xiaoying Credit Loans and Xiaoying Revolving Loans, net (Details)	12 Months Ended
Dec. 31, 2022 CNY (¥)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 CNY (¥)
Summary of significant accounting policies
Loan receivable from Xiaoying Housing Loans, net	¥ 3,810,393,225	$ 552,455,087	¥ 2,484,072,931
Accrued interest receivable	¥ 55,245,376	$ 8,009,827	¥ 26,080,407
Charges off policy of Loans receivables (in days)	60 days

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Name:	us-gaap_LoansAndLeasesReceivableNetReportedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant