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Commitments and Contingencies - Narrative - Environmental Reserves and Estimated Recoveries (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2017
Nov. 30, 2003
Site Contingency [Line Items]    
Non-reimbursable percentage of environmental costs 24.00%  
Northrop    
Site Contingency [Line Items]    
Current annual billing limitation $ 6,000,000  
Nontrade receivables $ 67,700,000  
Atlantic Research Corporation    
Site Contingency [Line Items]    
Pre-close environmental costs   $ 20,000,000.0
Various Environmental Matters    
Site Contingency [Line Items]    
Environmental remediation term 15 years