Revenues (Unrecognized Revenues Under Contract) (Details) $ in Millions	Sep. 30, 2020 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Unrecognized revenue	$ 6,370
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Unrecognized revenue	$ 1,070
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Unrecognized revenue	$ 2,760
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Unrecognized revenue	$ 1,790
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Unrecognized revenue	$ 744
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction period