Accounting Policies Summary of Significant Accounting Policies (Details) - USD ($)	Apr. 30, 2019	Jan. 31, 2019	Apr. 30, 2018	Jan. 31, 2018
Restricted Cash [Abstract]
Restricted Cash	$ 37,000,000	$ 34,000,000	$ 300,000,000	$ 300,000,000
Revenue from Contract with Customer [Abstract]
Receivables from transactions with customers, net	2,566,000,000		2,538,000,000
Deferred gift card revenue	$ 1,899,000,000		$ 1,932,000,000