v3.26.3
Cover
 6 Months Ended
Jun. 30, 2026
Entity Addresses [Line Items]  
Document Type S-4
Amendment Flag false
Entity Registrant Name Star Equity Holdings, Inc.
Entity Central Index Key 0001210708
Entity Primary SIC Number 7363
Entity Tax Identification Number 59-3547281
Entity Incorporation, State or Country Code DE
Entity Address, Address Line One 53 Forest Avenue
Entity Address, Address Line Two Suite 101
Entity Address, City or Town Old Greenwich
Entity Address, State or Province CT
Entity Address, Postal Zip Code 06870
City Area Code (203)
Local Phone Number 489-9500
Entity Filer Category Non-accelerated Filer
Entity Small Business true
Entity Emerging Growth Company false
Business Contact [Member]  
Entity Addresses [Line Items]  
Entity Address, Address Line One 53 Forest Avenue
Entity Address, Address Line Two Suite 101
Entity Address, City or Town Old Greenwich
Entity Address, State or Province CT
Entity Address, Postal Zip Code 06870
City Area Code (203)
Local Phone Number 489-9500
Contact Personnel Name Jeffrey E. Eberwein