Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011	Jul. 31, 2010
Income Taxes (Textuals)
Effective income tax rate	31.20%	34.00%	33.40%	32.50%
Tax benefit as a result of tax adjustments and tax settlements			$ 0	$ 3,096,000
Unrecognized Tax Benefits, Decreases Resulting from Current Period Tax Positions	$ 20,000,000		$ 20,000,000