Casualty, Environmental and Other Reserves - Narrative (Details)	3 Months Ended
	Mar. 31, 2021 USD ($) claim site	Dec. 31, 2020 USD ($)
All Contingencies Reserves [Line Items]
Total reserves	$ 318,000,000	$ 314,000,000
Casualty
All Contingencies Reserves [Line Items]
Total reserves	200,000,000	196,000,000
Self-insured retention amount, per occurrence	$ 75,000,000
Number of individual claims expected to exceed self insured retention amount | claim	0
Environmental
All Contingencies Reserves [Line Items]
Total reserves	$ 77,000,000	76,000,000
Environmental impaired sites | site	220
Other
All Contingencies Reserves [Line Items]
Total reserves	$ 41,000,000	$ 42,000,000