| Cover | Aug. 10, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 10, 2021 |
| Entity Registrant Name | HYLIION HOLDINGS CORP. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38823 |
| Entity Tax Identification Number | 82-2538002 |
| Entity Address, Address Line One | 1202 BMC Drive, Suite 100 |
| Entity Address, City or Town | Cedar Park |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 78613 |
| City Area Code | 833 |
| Local Phone Number | 495-4466 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value per share |
| Trading Symbol | HYLN |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001759631 |
| Amendment Flag | false |
