| Document and Entity Information | Jan. 19, 2022 |
| Document And Entity Information [Line Items] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001828183 |
| Document Type | 8-K |
| Document Period End Date | Jan. 19, 2022 |
| Entity Registrant Name | FORTRESS VALUE ACQUISITION CORP. IV |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-40219 |
| Entity Tax Identification Number | 85-3271127 |
| Entity Address, Address Line One | 1345 Avenue of the Americas |
| Entity Address, Address Line Two | 46th Floor |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10105 |
| City Area Code | (212) |
| Local Phone Number | 798-6100 |
| 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 |
| Units [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Units, each consisting of one share of Class A common stock and one-eighth of one redeemable warrant |
| Trading Symbol | FVIV.U |
| Security Exchange Name | NYSE |
| Common Class A [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Class A common stock, par value $0.0001 per share |
| Trading Symbol | FVIV |
| Security Exchange Name | NYSE |
| Redeemable Warrants [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Redeemable warrants, each whole warrant exercisable for one share of Class A common stock at an exercise price of $11.50 per share |
| Trading Symbol | FVIV WS |
| Security Exchange Name | NYSE |
