Business, Basis of Presentation and Significant Accounting Policies (Remaining Performance Obligations) (Narrative) (Details) $ in Billions	Sep. 30, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 5.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue from Contract with Customer [Abstract]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 1.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue recognition, remaining performance obligations, completion period (in months)	3 months