Revenues and Contract Costs - Schedule of Cost Incurred to Obtain or Fulfill Contracts with Customers (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Capitalized Contract Cost [Line Items]
Cost incurred to obtain or fulfill contracts with customers	$ 4,233	$ 4,489
Minimum
Capitalized Contract Cost [Line Items]
Deferred contract cost, amortization period	2 years
Maximum
Capitalized Contract Cost [Line Items]
Deferred contract cost, amortization period	5 years
Prepaid expenses and other
Capitalized Contract Cost [Line Items]
Cost incurred to obtain or fulfill contracts with customers	$ 2,428	2,578
Other assets
Capitalized Contract Cost [Line Items]
Cost incurred to obtain or fulfill contracts with customers	$ 1,805	$ 1,911