Revenue Recognition Contract Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Contract With Customer, Liability [Line Items]
Contract with Customer, Liability - Beginning of Period	$ 1,203	$ 1,331	$ 1,215	$ 1,397
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Change in Measure of Progress	14	12	116	138
Contract Liability Noncash Interest Expense Significant Financing Obligation	3	3	8	10
Contract with Customer, Liability, Revenue Recognized	(50)	(77)	(169)	(276)
Contract with Customer, Liability - End of Period	$ 1,170	$ 1,269	$ 1,170	$ 1,269