Business, Basis of Presentation and Significant Accounting Policies (Remaining Performance Obligations) (Narrative) (Details) $ in Billions	Mar. 31, 2021 USD ($)
Accounting Policies [Abstract]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 5.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Accounting Policies [Abstract]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 4.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year