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Stock-Based Compensation Plans (Details) (USD $)
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12 Months Ended | 12 Months Ended | 12 Months Ended | |||||||||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2012
2009 Plan
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May 21, 2009
2009 Plan
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Dec. 31, 2012
2009 Plan
Stock Options
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Dec. 31, 2011
2009 Plan
Stock Options
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Dec. 31, 2010
2009 Plan
Stock Options
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Dec. 31, 2012
1994 Plan
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Dec. 31, 2012
1994 Plan
Stock Options
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Dec. 31, 2011
1994 Plan
Stock Options
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Dec. 31, 2010
1994 Plan
Stock Options
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| Stock-Based Compensation Plans | ||||||||||||
| Common stock authorized for issuance under incentive plan | 4,199,822 | 1,269,822 | ||||||||||
| Common stock shares available for grant | 1,269,822 | |||||||||||
| Common stock, par value (in dollars per share) | $ 0.01 | $ 0.01 | $ 0.01 | |||||||||
| Common stock authorized under the new plan for issuance under incentive plan | 2,930,000 | |||||||||||
| Shares | ||||||||||||
| Options outstanding at the beginning of the period (in shares) | 247,403 | 126,484 | 1,112,959 | 2,072,217 | 2,836,254 | |||||||
| Exercised (in shares) | (407,784) | (43,265) | (23,908) | (364,519) | (930,391) | (729,381) | ||||||
| Granted (in shares) | 115,303 | 144,827 | 126,484 | 115,303 | 144,827 | 126,484 | ||||||
| Forfeited (in shares) | (11,887) | (28,610) | (28,867) | (34,656) | ||||||||
| Options outstanding at the end of the period (in shares) | 307,554 | 247,403 | 126,484 | 719,830 | 1,112,959 | 2,072,217 | ||||||
| Options exercisable at the end of the period (in shares) | 74,618 | 30,771 | 3,417 | 719,830 | 1,012,304 | 1,730,978 | ||||||
| Weighted average exercise price per share | ||||||||||||
| Options outstanding at the beginning of the period (in dollars per share) | $ 98.42 | $ 74.20 | $ 94.10 | $ 88.50 | $ 80.76 | |||||||
| Exercised (in dollars per share) | $ 85.09 | $ 75.75 | $ 68.21 | $ 82.43 | $ 57.87 | |||||||
| Granted (in dollars per share) | $ 133.16 | $ 115.83 | $ 74.20 | |||||||||
| Forfeited (in dollars per share) | $ 115.15 | $ 139.58 | $ 68.29 | $ 100.02 | ||||||||
| Options outstanding at the end of the period (in dollars per share) | $ 112.67 | $ 98.42 | $ 74.20 | $ 105.40 | $ 94.10 | $ 88.50 | ||||||
| Options exercisable at the end of the period (in dollars per share) | $ 97.46 | $ 81.54 | $ 74.20 | $ 105.40 | $ 98.62 | $ 93.60 | ||||||