| Document and Entity Information | Mar. 31, 2020 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 31, 2020 |
| Entity File Number | 0-18183 |
| Entity Registrant Name | G III APPAREL GROUP LTD /DE/ |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 41-1590959 |
| Entity Address, Address Line One | 512 Seventh Avenue |
| Entity Address, State or Province | NY |
| Entity Address, City or Town | New York |
| Entity Address, Postal Zip Code | 10018 |
| City Area Code | 212 |
| Local Phone Number | 403-0500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value per share |
| Trading Symbol | GIII |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000821002 |
| Amendment Flag | false |
