Casualty, Environmental and Other Reserves - Narrative (Details) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
	Jun. 01, 2018 USD ($)	Dec. 31, 2019 USD ($) claim site $ / shares	Sep. 30, 2019 $ / shares	Jun. 30, 2019 $ / shares	Mar. 31, 2019 $ / shares	Dec. 31, 2018 USD ($) $ / shares	Sep. 30, 2018 $ / shares	Jun. 30, 2018 $ / shares	Mar. 31, 2018 $ / shares	Dec. 31, 2019 USD ($) claim site $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 30, 2016 USD ($)
Loss Contingencies [Line Items]
Reserves		$ 305				$ 324				$ 305	$ 324	$ 374	$ 374
Earnings per share impact (in dollars per share) | $ / shares		$ 0.99	$ 1.08	$ 1.08	$ 1.02	$ 1.02	$ 1.05	$ 1.02	$ 0.78	$ 4.18	$ 3.86	$ 6.01
Casualty
Loss Contingencies [Line Items]
Reserves		$ 187				$ 199				$ 187	$ 199	$ 228	229
Individual claims expected to exceed self-insured retention amount | claim		0								0
Casualty | Minimum
Loss Contingencies [Line Items]
Self-insured retention amount per injury	$ 50
Casualty | Maximum
Loss Contingencies [Line Items]
Self-insured retention amount per injury	$ 75
Personal Injury
Loss Contingencies [Line Items]
Reserves		$ 129				143				$ 129	143
Environmental
Loss Contingencies [Line Items]
Reserves		$ 74				80				$ 74	80	90	95
Environmental impaired sites | site		220								220
Other
Loss Contingencies [Line Items]
Reserves		$ 44				$ 45				$ 44	$ 45	$ 56	$ 50