Annual report pursuant to Section 13 and 15(d)

Stock-Based Employee Compensation (Details 4)

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Stock-Based Employee Compensation (Details 4) (USD $)
12 Months Ended
Feb. 28, 2013
Feb. 29, 2012
Feb. 28, 2011
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Weighted average grant-date fair value of stock options granted $ 8.39 $ 7.41 $ 6.19
Total fair value of stock options vested $ 22,421,290 $ 31,140,184 $ 37,360,244
Total intrinsic value of stock options exercised 95,033,640 23,139,194 33,134,478
Tax benefit realized from stock options exercised $ 25,274,158 $ 10,835,473 $ 7,810,198