Basis of Presentation and Nature of Operations (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation and Nature of Operations	Aerojet Rocketdyne Holdings, Inc. ("Aerojet Rocketdyne Holdings" or the "Company") has prepared the accompanying unaudited condensed consolidated financial statements, including the accounts of the Company and its 100% owned and majority owned subsidiaries, in accordance with the instructions to Form 10-Q. The December 31, 2019, condensed consolidated balance sheet was derived from audited financial statements, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America ("GAAP"). These interim financial statements should be read in conjunction with the financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. The Company believes the accompanying unaudited condensed consolidated financial statements reflect all adjustments, including normal recurring accruals, necessary for a fair statement of its financial position, results of operations, and cash flows for the periods presented. All significant intercompany balances and transactions have been eliminated in consolidation. The preparation of the unaudited condensed consolidated financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the unaudited condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. In addition, the operating results for interim periods may not be indicative of the results of operations for a full year. The Company’s operations are organized into two segments: Aerospace and Defense — includes the operations of the Company’s wholly-owned subsidiary Aerojet Rocketdyne, Inc. ("Aerojet Rocketdyne"), a leading technology-based designer, developer and manufacturer of aerospace and defense products and systems for the United States ("U.S.") government, including the Department of Defense ("DoD"), the National Aeronautics and Space Administration ("NASA"), and major aerospace and defense prime contractors. Real Estate — includes the activities of the Company’s wholly-owned subsidiary Easton Development Company, LLC ("Easton") related to the re-zoning, entitlement, sale, and leasing of the Company’s excess real estate assets. The year of the Company's subsidiary, Aerojet Rocketdyne, ends on the last Saturday in December. A detailed description of the Company’s significant accounting policies can be found in the Company’s most recent Annual Report on Form 10-K for the year ended December 31, 2019. During the three months ended March 31, 2020, the Company’s financial results and operations were not materially impacted by the coronavirus ("COVID-19") pandemic. As a defense industrial-base U.S. government contractor, the Company is considered an essential business by the U.S. and state governments and it continues to operate as such during the COVID-19 pandemic. The extent to which the COVID-19 pandemic impacts the Company’s financial results and operations for 2020 and beyond will depend on future developments that are highly uncertain and cannot be predicted at this time. The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of the date of issuance of this Quarterly Report on Form 10-Q. These estimates may change, as new events occur and additional information is obtained. Actual results could differ materially from these estimates under different assumptions or conditions.
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board issued guidance requiring a customer in a cloud computing service arrangement to follow the internal-use software guidance in order to determine which implementation costs to defer and recognize as an asset. The Company adopted this new standard as of January 1, 2020, on a prospective basis and the adoption of this guidance did not have a material impact on the Company's financial position, results of operations, or cash flows.
Revenue Recognition	Revenue Recognition In the Company’s Aerospace and Defense segment, the majority of revenue is earned from long-term contracts to design, develop, and manufacture aerospace and defense products for, and provide related services to, the Company’s customers, including the U.S. government and major aerospace and defense prime contractors. In the Company’s Aerospace and Defense segment, the timing of revenue recognition, customer invoicing, and collections produces accounts receivable, contract assets, and contract liabilities in the unaudited condensed consolidated balance sheets.
Environmental Reserves	Environmental Reserves