| Document And Entity Information | Dec. 04, 2020 |
| Document Information [Line Items] | |
| Entity, Registrant Name | SEACOR Holdings Inc. |
| Document, Type | 8-K |
| Document, Period End Date | Dec. 4, 2020 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 1-12289 |
| Entity, Tax Identification Number | 13-3542736 |
| Entity, Address, Address Line One | 2200 Eller Drive |
| Entity, Address, City or Town | Fort Lauderdale |
| Entity, Address, State or Province | FL |
| Entity, Address, Postal Zip Code | 33316 |
| City Area Code | 954 |
| Local Phone Number | 523-2200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | CKH |
| Security Exchange Name | NYSE |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000859598 |
