Employee and Director Stock Plans - Options Outstanding (Details) - $ / shares shares in Millions	Jan. 31, 2019	Jan. 31, 2018
Number of securities to be issued upon exercise or vesting of outstanding options and awards (in shares)	5.1
Weighted-average exercise price of outstanding options (in dollars per share)	$ 23.95	$ 40.49
Number of securities remaining available for future issuance under equity compensation plans (excluding securities reflected in column (a)) (in shares)	27.6
Equity Compensation Plans Approved by Security Holders
Number of securities to be issued upon exercise or vesting of outstanding options and awards (in shares)	5.1
Weighted-average exercise price of outstanding options (in dollars per share)	$ 23.95
Number of securities remaining available for future issuance under equity compensation plans (excluding securities reflected in column (a)) (in shares)	27.6
ESP Plan
Number of securities remaining available for future issuance under equity compensation plans (excluding securities reflected in column (a)) (in shares)	8.1