| Document and Entity Information | Jan. 01, 2025 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 01, 2025 |
| Entity File Number | 001-42113 |
| Entity Registrant Name | SEAPORT ENTERTAINMENT GROUP INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 99-0947924 |
| Entity Address State Or Province | NY |
| Entity Address, Address Line One | 199 Water Street |
| Entity Address, Adress Line Two | 28th Floor |
| Entity Address, City or Town | NewYork |
| Entity Address, Postal Zip Code | 10038 |
| City Area Code | 212 |
| Local Phone Number | 732-8257 |
| Title of 12(b) Security | Common stock, par value $0.01 per share |
| Trading Symbol | SEG |
| Security Exchange Name | NYSEAMER |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
| Entity Central Index Key | 0002009684 |
| Amendment Flag | false |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
