AR1 Research and Development (Details) - U.S. Air Force [Member] - U.S. Government Contractual Arrangements [Member] - Liquid Booster Engine Development Project [Member] - USD ($) $ in Millions	1 Months Ended
Mar. 31, 2016	Feb. 29, 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
AR1 research and development	$ 33.1
AR1 R&D costs net of reimbursements	65.2
Research and development expense, not charged to contractual arrangements	(32.1)
AR1 research and development expense, gross	75.6
Aerojet Rocketdyne and United Launch Alliance [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Agreement value		$ 804.0
Intended initial contribution		57.7
Potential total contribution		$ 536.0
U.S. Air Force [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Investment percentage of total funding required		66.67%
Intended initial contribution		$ 115.3
Customer funding to offset costs incurred, amount collected	(6.9)
Aerojet Rocketdyne and Partners [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential total contribution		$ 268.0
U.S. Air Force and United Launch Alliance [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Customer funding to offset costs incurred	10.4
United Launch Alliance [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Customer funding to offset costs incurred, amount collected	$ (3.5)

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Research and Development Expense, Net of Reimbursements

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The net amount of research and development costs incurred for a fixed-price, best-efforts research and development cost-sharing arrangement with the Federal Government.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 912
-SubTopic 730
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6472174&loc=d3e58812-109433

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

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