Stockholders' Equity (Details) - $ / shares	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015	Sep. 30, 2016
Stockholders Equity Note [Line Items]
Preferred stock, shares authorized (in shares)	2,000,000	2,000,000.0
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common Stock Repurchase Program
Stockholders Equity Note [Line Items]
Repurchase and retirement of common shares (in shares)	9,700,000	8,500,000	6,900,000
Average repurchase price per share (usd per share)	$ 64.73	$ 53.58	$ 53.83
Common Stock shares remained available for repurchase under repurchase plans (in shares)	26,600,000
Additional shares authorized for repurchase (in shares)				30,000,000