Cover - shares	9 Months Ended
	Sep. 30, 2021	Oct. 18, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	1-01520
Entity Registrant Name	Aerojet Rocketdyne Holdings, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	34-0244000
Entity Address, Address Line One	222 N. Pacific Coast Highway
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
Title of 12(b) Security	Common stock, $0.10 par value
Trading Symbol	AJRD
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		80,500,624
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000040888
Current Fiscal Year End Date	--12-31