Revenue Recognition Contract Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Contract With Customer, Liability [Line Items]
Contract with Customer, Liability - Beginning of Period	$ 1,189	$ 1,335	$ 1,215	$ 1,397
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Change in Measure of Progress	74	93	102	126
Contract Liability Noncash Interest Expense Significant Financing Obligation	2	3	5	7
Contract with Customer, Liability, Revenue Recognized	(62)	(100)	(119)	(199)
Contract with Customer, Liability - End of Period	$ 1,203	$ 1,331	$ 1,203	$ 1,331