Annual report pursuant to Section 13 and 15(d)

STOCK INCENTIVE AND STOCK OPTION PLANS (Details 2)

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STOCK INCENTIVE AND STOCK OPTION PLANS (Details 2) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Stock option plan activity      
Balance, at the beginning of the period (in shares) 1,243,037 1,073,595 896,830
Granted (in shares) 321,945 316,159 387,250
Exercised (in shares) (241,815) (134,520) (195,530)
Forfeited (in shares) (13,999) (12,197) (8,555)
Expired (in shares)     (6,400)
Balance, at the end of the period (in shares) 1,309,168 1,243,037 1,073,595
Exercisable (in shares) 785,869 721,210 222,110
Weighted-average Exercise Price at the beginning of the period (in dollars per share) $ 59.02 $ 37.92 $ 22.55
Weighted-average Exercise Price Granted (in dollars per share) $ 119.34 $ 115.71 $ 62.74
Weighted-average Exercise Price Exercised (in dollars per share) $ 31.73 $ 23.93 $ 17.36
Weighted-average Exercise Price Forfeited (in dollars per share) $ 67.86 $ 57.68 $ 41.54
Weighted-average Exercise Price Expired (in dollars per share)     $ 9.33
Weighted-average Exercise Price at the end of the period (in dollars per share) $ 78.80 $ 59.02 $ 37.92
Weighted-average Exercise Price Exercisable (in dollars per share) $ 51.40 $ 38.75 $ 26.36
Weighted-average remaining contractual life of options outstanding 7 years 3 months 18 days    
Weighted-average remaining contractual life of options exercisable 6 years 3 months 4 days 6 years 3 months 5 years 4 months 24 days
Aggregate intrinsic value of options outstanding (in dollars) $ 44,192,177    
Aggregate intrinsic value of options exercisable (in dollars) 44,176,663 37,526,500 18,683,972
Weighted average grant date fair value of options granted (in dollars per share) $ 54.25 $ 51.23 $ 27.45
Total intrinsic value of options exercised (in dollars) $ 19,000,000 $ 12,000,000 $ 13,000,000