Revenue Recognition Contract Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Revenue Recognition [Abstract]
Contract with Customer, Asset, after Allowance for Credit Loss	$ 42	$ 31	$ 42	$ 31	$ 30	$ 8	$ 17	$ 4
Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Change in Measure of Progress	36	14	105	53
Contract with Customer, Asset, Reclassified to Receivable	$ (24)	$ 0	$ (71)	$ (26)