STAR EQUITY HOLDINGS, INC. CONDENSED CONSOLIDATED STATEMENTS OF MEZZANINE EQUITY AND STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Perpetual Preferred Stock	Common stock	Treasury Stock	Additional paid-in capital	Accumulated deficit
Beginning balance (shares) at Dec. 31, 2020		1,916	4,798
Beginning balance at Dec. 31, 2020	$ 18,429	$ 21,500	$ 0	$ (5,728)	$ 149,143	$ (124,986)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	131				131
Shares issued under stock incentive plans, net of shares withheld for employee taxes (in shares)			3
Shares issued under stock incentive plans, net of shares withheld for employee taxes	(5)				(5)
Accrued dividends on redeemable preferred stock	(479)	$ 479			(479)
Proceeds from exercise of warrants (in shares)			220
Proceeds from the exercise of warrants	493				493
Net (loss) income	5,432					5,432
Ending balance (shares) at Mar. 31, 2021		1,916	5,021
Ending balance at Mar. 31, 2021	24,001	$ 21,979	$ 0	(5,728)	149,283	(119,554)
Beginning balance (shares) at Dec. 31, 2021		1,916	5,805
Beginning balance at Dec. 31, 2021	16,754	$ 18,988	$ 0	(5,728)	150,451	(127,969)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	144				144
Shares issued under stock incentive plans, net of shares withheld for employee taxes (in shares)			49
Shares issued under stock incentive plans, net of shares withheld for employee taxes	(3)				(3)
Accrued dividends on redeemable preferred stock	(479)	479			(479)
Preferred stock dividends paid	0	$ (479)
Equity issuance costs	(450)				(450)
Proceeds from sale and exercise of common stock, over allotment options and warrants (in shares)			9,175
Proceeds from the sale of common stock, warrants, and exercise of over allotment options	13,198		$ 1		13,197
Net (loss) income	(3,701)					(3,701)
Ending balance (shares) at Mar. 31, 2022		1,916	15,029
Ending balance at Mar. 31, 2022	$ 25,463	$ 18,988	$ 1	$ (5,728)	$ 162,860	$ (131,670)