Financing Activities (Details) shares in Millions, $ in Millions	3 Months Ended
	Apr. 30, 2016 USD ($) shares
Financing Activities [Abstract]
Stock Repurchased During Period, Shares | shares	3.0
Stock Repurchased During Period, Value	$ 129
Stock Repurchase Program, Authorized Amount	1,500
Stock Repurchase Program, Remaining Authorized Repurchase Amount	1,903
Line of Credit Facility, Current Borrowing Capacity	1,500
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,750