| Document and Entity Information | Oct. 04, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 4, 2021 |
| Entity Registrant Name | ALTA EQUIPMENT GROUP INC. |
| Entity Central Index Key | 0001759824 |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38864 |
| Entity Tax Identification Number | 83-2583782 |
| Entity Address, Address Line One | 13211 Merriman Road |
| Entity Address, City or Town | Livonia |
| Entity Address, State or Province | MI |
| Entity Address, Postal Zip Code | 48150 |
| City Area Code | 248 |
| Local Phone Number | 449-6700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Common Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common stock, $0.0001 par value per share |
| Trading Symbol | ALTG |
| Security Exchange Name | NYSE |
| Preferred Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares |
| Trading Symbol | ALTG PRA |
| Security Exchange Name | NYSE |
