Revenue Recognition (Narrative) (Details) $ in Billions	Jul. 31, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 2.2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-08-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation percentage	74.00%
Performance obligation, expected timing of satisfaction	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-08-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 0.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation percentage	26.00%
Performance obligation, expected timing of satisfaction