CONDENSED PARENT COMPANY ONLY FINANCIAL INFORMATION - CONDENSED STATEMENTS OF FINANCIAL CONDITION (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
ASSETS
Investment securities available-for-sale, at fair value	$ 79,602	$ 88,339
Other assets	2,254	470
TOTAL ASSETS	263,324	285,610
LIABILITIES
Other liabilities	558	1,244
TOTAL LIABILITIES	174,850	187,057
SHAREHOLDERS' EQUITY
Common Stock, Value, Issued	53	53
Additional paid-in capital	51,062	50,802
Unallocated common stock held by benefit plans	(6,307)	(4,179)
Retained earnings	52,740	52,560
Accumulated other comprehensive income (loss)	(9,074)	(683)
TOTAL SHAREHOLDERS' EQUITY	88,474	98,553	$ 50,752
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	263,324	285,610
Catalyst Bancorp, Inc.
ASSETS
Cash and due from banks	6,603	9,592
Investment in bank subsidiary	70,550	77,402
Investment securities available-for-sale, at fair value	10,969	11,518
Other assets	366	41
TOTAL ASSETS	88,488	98,553
LIABILITIES
Other liabilities	14
TOTAL LIABILITIES	14
SHAREHOLDERS' EQUITY
Common Stock, Value, Issued	53	53
Additional paid-in capital	51,062	50,802
Unallocated common stock held by benefit plans	(6,307)	(4,179)
Retained earnings	52,740	52,560
Accumulated other comprehensive income (loss)	(9,074)	(683)
TOTAL SHAREHOLDERS' EQUITY	88,474	98,553
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 88,488	$ 98,553