Stockholders Equity Stockholders' Equity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Stockholders Equity Note [Line Items]
Preferred stock, shares authorized	2.0	2.0
Repurchase and retirement of common shares (in shares)	9.7	9.0	2.7
Common Stock Repurchase Program
Stockholders Equity Note [Line Items]
Repurchased shares of its common stock on the open market, average repurchase price per share	33.71	31.13	23.63
Common Stock shares remained available for repurchase under repurchase plans	14.7
Common Stock [Member]
Stockholders Equity Note [Line Items]
Repurchase and retirement of common shares (in shares)	9.7	9.0	2.7
Repurchased shares of its common stock on the open market, value	211.0	138.3	36.4
Retained Earnings [Member]
Stockholders Equity Note [Line Items]
Repurchased shares of its common stock on the open market, value	116.4	142.0	26.8