Revenues and Contract Costs - Contract with Customer, Asset and Liability (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 01, 2020	Dec. 31, 2019	Jan. 01, 2019
Disaggregation of Revenue [Line Items]
Contract asset	$ 993	$ 1,059	$ 993	$ 1,059	$ 1,150	$ 1,150	$ 1,003
Contract liability	5,275	4,946	5,275	4,946	$ 5,307	5,307	$ 4,943
Revenue recognized related to contract liabilities existing	204	$ 194	4,000	$ 3,900
Prepaid expenses and other
Disaggregation of Revenue [Line Items]
Contract asset	762		762			848
Other assets
Disaggregation of Revenue [Line Items]
Contract asset	231		231			302
Other current liabilities
Disaggregation of Revenue [Line Items]
Contract liability	4,636		4,636			4,651
Other liabilities
Disaggregation of Revenue [Line Items]
Contract liability	$ 639		$ 639			$ 656