Business and Summary of Significant Accounting Policies - New Accounting Standards (Details) - Scenario, Forecast - Accounting Standards Update 2014-09 $ in Millions	12 Months Ended
	Jan. 31, 2019 USD ($)
Minimum | Deferred Revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expected impact of new accounting pronouncement	$ (80)
Minimum | Capitalized Sales Commission Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expected impact of new accounting pronouncement	(102)
Maximum | Deferred Revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expected impact of new accounting pronouncement	(100)
Maximum | Capitalized Sales Commission Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expected impact of new accounting pronouncement	$ (112)