Financial Instruments - Available for Sale Securities (Detail) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Derivative [Line Items]
Cost Method Investments	$ 117.2	$ 104.3
Other than Temporary Impairment Losses, Investments	1.3	0.2
Available-for-sale securities gross gains (losses)	1.5	0.1	$ 0.7
Proceeds from Sale and Maturity of Marketable Securities	$ 2,300.0	$ 1,700.0