Employee Stock and Savings Plans Weighting of elements included in volatility assumption (Details)	12 Months Ended
	Jan. 31, 2013
Common Stock [Member]
Weighting of elements used in determining volatility assumption	20.00%
Exchange Traded Options [Member]
Weighting of elements used in determining volatility assumption	15.00%
Common Stock [Member]
Weighting of elements used in determining volatility assumption	35.00%
Exchange Traded Options [Member]
Weighting of elements used in determining volatility assumption	30.00%