FAIR VALUE MEASUREMENTS - Assets measured at fair value on a recurring basis (Details) - USD ($)	Mar. 31, 2026	Dec. 31, 2025
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	$ 5,469,258	$ 5,538,692
U.S. government agencies
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	1,428,897	1,437,836
Municipal securities
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	2,834,451	2,836,036
Recurring
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	5,469,258	5,538,692
Total Fair Value Measurements	5,469,258	5,538,692
Recurring \| U.S. government agencies
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	1,428,897	1,437,836
Recurring \| Mortgage-backed securities and collateralized mortgage obligation bonds
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	1,205,910	1,264,820
Recurring \| Municipal securities
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	2,834,451	2,836,036
Recurring \| Level 2
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	5,469,258	5,538,692
Total Fair Value Measurements	5,469,258	5,538,692
Recurring \| Level 2 \| U.S. government agencies
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	1,428,897	1,437,836
Recurring \| Level 2 \| Mortgage-backed securities and collateralized mortgage obligation bonds
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	1,205,910	1,264,820
Recurring \| Level 2 \| Municipal securities
FAIR VALUE MEASUREMENTS
Available-for-sale debt securities	$ 2,834,451	$ 2,836,036

CSB Financial Inc. 10-Q