Accounting Policies Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	Oct. 31, 2019	Jan. 31, 2019	Oct. 31, 2018	Jan. 31, 2018
Restricted Cash [Abstract]
Restricted Cash	$ 25	$ 34	$ 30	$ 300
Revenue from Contract with Customer [Abstract]
Receivables from transactions with customers, net	2,618	2,538
Deferred gift card revenue	$ 1,863	$ 1,932