CONDENSED PARENT COMPANY ONLY FINANCIAL INFORMATION - CONDENSED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 1,927	$ (703)
Adjustments to reconcile net income to net cash provided by operating activities:
Investment securities amortization, net	409	208
(Increase) decrease in other assets	456	(86)
Net cash provided by operating activities	3,428	857
Activity in available-for-sale securities:
Proceeds from maturities, calls, and paydowns	8,554	10,177
Purchases	(77,545)	(16,719)
Net cash used in investing activities	(46,589)	(313)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of common stock, net of costs	50,835
Purchase of stock for ESOP	(4,232)
Net cash provided by financing activities	58,800	6,792
NET INCREASE IN CASH AND CASH EQUIVALENTS	15,639	7,336
CASH AND CASH EQUIVALENTS, beginning of period	25,245
CASH AND CASH EQUIVALENTS, end of period	40,884	$ 25,245
Catalyst Bancorp, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	1,927
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiary	(1,949)
Investment securities amortization, net	2
(Increase) decrease in other assets	(26)
Net cash provided by operating activities	(46)
CASH FLOWS FROM INVESTING ACTIVITIES
Capital injection into subsidiary from stock offering	(25,442)
Payments received on ESOP loan	72
Activity in available-for-sale securities:
Proceeds from maturities, calls, and paydowns	37
Purchases	(11,632)
Net cash used in investing activities	(36,965)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of common stock, net of costs	50,835
Purchase of stock for ESOP	(4,232)
Net cash provided by financing activities	46,603
NET INCREASE IN CASH AND CASH EQUIVALENTS	9,592
CASH AND CASH EQUIVALENTS, end of period	$ 9,592