| Cover | Sep. 26, 2023 |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 26, 2023 |
| Entity File Number | 001-40214 |
| Entity Registrant Name | FAST Acquisition Corp. II |
| Entity Central Index Key | 0001839824 |
| Entity Tax Identification Number | 86-1258014 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 109 Old Branchville Road |
| Entity Address, City or Town | Ridgefield |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06877 |
| City Area Code | 201 |
| Local Phone Number | 956-1969 |
| Written Communications | false |
| Soliciting Material | false |
| 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, each consisting of one share of Class A common stock and one-quarter of one redeemable warrant | |
| Title of 12(b) Security | Units, each consisting of one share of Class A common stock and one-quarter of one redeemable warrant |
| Trading Symbol | FZT.U |
| Security Exchange Name | NYSE |
| Class A common stock, par value $0.0001 per share | |
| Title of 12(b) Security | Class A common stock, par value $0.0001 per share |
| Trading Symbol | FZT |
| Security Exchange Name | NYSE |
| Redeemable warrants, each warrant exercisable for one share of Class A common stock, each at an exercise price of $11.50 per share | |
| Title of 12(b) Security | Redeemable warrants, each warrant exercisable for one share of Class A common stock, each at an exercise price of $11.50 per share |
| Trading Symbol | FZT WS |
| Security Exchange Name | NYSE |
