Commitments and Contingencies - Additional Information - Environmental Reserves and Estimated Recoveries (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Aug. 31, 2010	May 31, 2014
Site Contingency [Line Items]
Environmental remediation costs, recognition period		15 years
Pre-Close Environmental Costs		$ 20.0
Percentage of environmental costs	12.00%
Increasing percentage of environmental costs	37.00%
Aerojet Rocketdyne- BPOU [Member]
Site Contingency [Line Items]
Project agreement expiration year		2017
Northrop Agreement [Member]
Site Contingency [Line Items]
Current annual billing limitation		6,000,000
Total reimbursable costs under the Northrop Agreement		189.7
Environmental costs above the cumulative limitation		$ 24.9