Summary of Significant Accounting Policies - Recently Issued Accounting Standards (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2020 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)
Recently issued accounting standards
Retained earnings	$ 3,983	$ 3,727
Selling, general and administrative expenses	336	314	$ 309
Miscellaneous, net	2	(3)	(5)
Accumulated other comprehensive loss	(440)	$ (410)	(354)
ROU assets	446				$ 460
Total operating lease liability	$ 483				$ 498
ASU 2016-01
Recently issued accounting standards
Retained earnings						$ 7
Accumulated other comprehensive loss						$ (7)
ASU 2018-02
Recently issued accounting standards
Retained earnings			45
Accumulated other comprehensive loss			$ (45)
ASU 2016-13 | Forecast | Maximum
Recently issued accounting standards
Retained earnings				$ 5
Designated as hedge
Derivative commodity instruments
Number of derivative agreements | item	0