Segments - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Number of operating segments | segment	2
Operating revenue	$ 17,095	$ 47,007	$ 44,438
Intersegment Sales/Other | Exchanged products
Business Acquisition [Line Items]
Operating revenue	$ (1,472)	$ (3,963)	$ (3,596)