Revenue Recognition (Narrative) (Details) $ in Billions	Jan. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 2.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-02-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation percentage	72.00%
Performance obligation, expected timing of satisfaction	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-02-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 0.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation percentage	28.00%
Performance obligation, expected timing of satisfaction