Revenues and Contract Costs - Contract with Customer, Asset and Liability (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2020	Dec. 31, 2019	Jan. 01, 2019
Disaggregation of Revenue [Line Items]
Contract asset	$ 1,135	$ 1,021	$ 1,150	$ 1,150	$ 1,003
Contract liability	5,347	4,973	$ 5,307	5,307	$ 4,943
Revenue recognized related to contract liabilities existing	3,800	$ 3,700
Prepaid expenses and other
Disaggregation of Revenue [Line Items]
Contract asset	844			848
Other assets
Disaggregation of Revenue [Line Items]
Contract asset	291			302
Other current liabilities
Disaggregation of Revenue [Line Items]
Contract liability	4,675			4,651
Other liabilities
Disaggregation of Revenue [Line Items]
Contract liability	$ 672			$ 656