Commitments and Contingencies - Narrative - Environmental Reserves and Estimated Recoveries (Details) - USD ($)	3 Months Ended	4 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Nov. 30, 2015	Nov. 30, 2003
Site Contingency [Line Items]
Pre-close environmental costs	$ 20,000,000
Non-reimbursable percentage of environmental costs				24.00%
Northrop [Member]
Site Contingency [Line Items]
Current annual billing limitation	$ 6,000,000		$ 6,000,000
Atlantic Research Corporation [Member]
Site Contingency [Line Items]
Pre-close environmental costs					$ 20,000,000.0
Atlantic Research Corporation [Member] | Scenario, Forecast [Member]
Site Contingency [Line Items]
Pre-close environmental costs		$ 20,000,000
Various Environmental Matters [Member]
Site Contingency [Line Items]
Environmental remediation term			15 years	15 years