| Document and Entity Information | Dec. 19, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0000040888 |
| Document Type | 8-K |
| Document Period End Date | Dec. 19, 2020 |
| Entity Registrant Name | AEROJET ROCKETDYNE HOLDINGS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-01520 |
| Entity Tax Identification Number | 34-0244000 |
| Entity Address, Address Line One | 222 N. Pacific Coast Highway, Suite 500 |
| Entity Address, Address Line Two | Suite 500 |
| Entity Address, City or Town | El Segundo |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90245 |
| City Area Code | (310) |
| Local Phone Number | 252-8100 |
| Written Communications | false |
| Soliciting Material | true |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common stock, $0.10 par value |
| Trading Symbol | AJRD |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
