Business, Basis of Presentation and Significant Accounting Policies (Remaining Performance Obligations) (Narrative) (Details) $ in Billions	Mar. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 5.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue from Contract with Customer [Abstract]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 4.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue recognition, remaining performance obligations, completion period (in months)	9 months