Revenues (Changes) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Significant changes to contract liabilities
Total contract liabilities, at beginning of period	$ 529	$ 486
Decrease due to recognition of revenues for goods and services	(153)	(83)
Increase due to goods and services transferred over time	108	102
Total contract liabilities, at end of period	$ 484	$ 505