Earnings Per Share (Shares Repurchased) (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended			1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	Dec. 31, 2013 Accelerated Share Repurchase (ASR)	Jan. 31, 2014 Accelerated Share Repurchase (ASR)	Jan. 31, 2014 Accelerated Share Repurchase (ASR)
Equity, Class of Treasury Stock [Line Items]
Agreement to repurchase shares, amount				$ 300,000,000
Number of shares repurchased and retired				5.6		5.6
Amount paid to repurchase outstanding shares	319,000,000	22,000,000	471,000,000	300,000,000
Percentage of total outstanding shares repurchased				85.00%
Value of initial shares repurchased	319,000,000	22,000,000	478,000,000		255,000,000
Forward contract indexed to our common stock					$ 45,000,000