Commitments and Contingencies - Summary of Pre-Close Environmental Costs (Details) $ in Millions	6 Months Ended
Jun. 30, 2016 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Pre-Close Environmental Costs	$ 20.0
Amount spent through June 30, 2016	(19.2)
Amount included as a component of reserves for environmental remediation costs in the unaudited condensed consolidated balance sheet as of June 30, 2016	(0.8)
Remaining Pre-Close Environmental Costs	$ 0.0

Environmental Remediation Costs Included In Environmental Reserve

No definition available.

Name:	ajrd_EnvironmentalRemediationCostsIncludedInEnvironmentalReserve
Namespace Prefix:	ajrd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration