Revenue - Recognized (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,167	$ 3,084	$ 8,613	$ 8,874
Over time
Disaggregation of Revenue [Line Items]
Revenue recognized	1,495	1,474	4,409	4,335
Point in time
Disaggregation of Revenue [Line Items]
Revenue recognized	$ 1,672	$ 1,610	$ 4,204	$ 4,539