Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2011	Oct. 31, 2010	Oct. 31, 2011	Oct. 31, 2010
Income Taxes (Textual)
Effective income tax rate	33.90%	34.90%	33.60%	33.20%
Tax benefit as a result of tax adjustments and tax settlements				$ 3,096,000
Unrecognized Tax Benefits, Decreases Resulting from Current Period Tax Positions	$ 20,000,000		$ 20,000,000