Summary of significant accounting policies - Loan receivable from Xiaoying Housing Loans, net (Details)	12 Months Ended
Dec. 31, 2025 CNY (¥)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 CNY (¥)	Dec. 31, 2023 CNY (¥)	Dec. 31, 2025 USD ($)
Summary of significant accounting policies
Allowance for loans receivable	¥ 236,233,265		¥ 175,820,629	¥ 188,719,449	$ 33,780,908
Loan receivable from Xiaoying, net	5,298,631,388		4,828,316,995		757,694,211
Allowance for loans receivable at beginning of the year	175,820,629	$ 25,142,016	188,719,449	106,479,154
(Reversal of) Provision for loans receivable from Xiaoying Credit Loans and other loans (net of recovery)	340,217,158	48,650,407	225,815,327	233,350,276
Charge-offs	279,804,522	40,011,515	238,714,147	151,109,981
Allowance for loans receivable at end of the year	236,233,265	33,780,908	175,820,629	188,719,449
Loans receivable, gross	5,534,864,653		5,004,137,624		$ 791,475,119
Recoveries of charge-off of loans receivables	¥ 27,672,522	$ 3,957,118	¥ 9,251,001	¥ 13,488,360

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

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+ Details