Cover
| Cover | Aug. 20, 2020 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 20, 2020 |
| Entity File Number | 001-38703 |
| Entity Registrant Name | GRAF INDUSTRIAL CORP. |
| Entity Central Index Key | 0001745317 |
| Entity Tax Identification Number | 83-1138508 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 118 Vintage Park Blvd. |
| Entity Address, Address Line Two | Suite W-222 |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77070 |
| City Area Code | 310 |
| Local Phone Number | 745-8669 |
| Written Communications | false |
| Soliciting Material | true |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| Units [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Units, each consisting of one share of common stock and one redeemable warrant |
| Trading Symbol | GRAF.U |
| Security Exchange Name | NYSE |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common stock, $0.0001 par value per share |
| Trading Symbol | GRAF |
| Security Exchange Name | NYSE |
| Warrants [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants, each exercisable for three-quarters of one share of common stock |
| Trading Symbol | GRAF WS |
| Security Exchange Name | NYSE |