Financial Instruments - Available for Sale Securities (Detail) - USD ($)	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014	Nov. 12, 2015
Derivative [Line Items]
Cost Method Investments	$ 104,300,000	$ 52,600,000
Other than Temporary Impairment Losses, Investments	200,000	19,200,000.0
Available-for-sale securities gross gains (losses)	100,000	700,000	$ (200,000)
Proceeds from Sale and Maturity of Marketable Securities	$ 1,700,000,000	$ 1,200,000,000
FIT AG
Derivative [Line Items]
Cost Method Investments				$ 27,400,000