Commitments and Contingencies - Narrative - Environmental Reserves and Estimated Recoveries (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Site Contingency [Line Items]
Environmental remediation cost expected period (years)	15 years
Non-reimbursable percentage of environmental costs	12.00%
Northrop
Site Contingency [Line Items]
Percentage of environmental remediation costs recoverable	88.00%
Current annual billing limitation	$ 6.0
Reimbursable remediation cost	$ 189.7