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Common Stock (Table) | 12 Months Ended
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Dec. 31, 2011
Common Stock [Abstract] |
Summary of stock options |
|  | Years Ended December 31, |
|  | 2011 |  |  | 2010 |  |  | 2009 |
|  | Number of Shares |  |  | Average Exercise Price |  |  | Number of Shares |  |  | Average Exercise Price |  |  | Number of Shares |  |  | Average Exercise Price |
Shares under option at beginning of year |  |  | 11,039,544 |  |  | $ | 38.01 |  |  |  | 10,255,982 |  |  | $ | 34.19 |  |  |  | 7,547,822 |  |  | $ | 37.24 |
Granted |  |  | 2,277,946 |  |  |  | 79.68 |  |  |  | 3,485,283 |  |  |  | 44.03 |  |  |  | 3,234,400 |  |  |  | 26.03 |
Cancelled |  |  | (241,174 | ) |  |  | 40.20 |  |  |  | (232,488 | ) |  |  | 40.53 |  |  |  | (156,356 | ) |  |  | 29.79 |
Exercised |  |  | (2,594,566 | ) |  |  | 36.84 |  |  |  | (2,469,233 | ) |  |  | 30.35 |  |  |  | (369,884 | ) |  |  | 40.86 |
Shares under option at end of year |  |  | 10,481,750 |  |  | $ | 47.20 |  |  |  | 11,039,544 |  |  | $ | 38.01 |  |  |  | 10,255,982 |  |  | $ | 34.19 |
Exercisable at end of year |  |  | 5,073,965 |  |  | $ | 38.47 |  |  |  | 5,067,186 |  |  | $ | 36.31 |  |  |  | 5,308,465 |  |  | $ | 33.14 |
Summary of stock option outstanding information |
Range of Exercise Price |  | Weighted-Avg Remaining Contractual Life |  |  | Options Outstanding |  |  | Options Exercisable |
|  | Shares |  |  | Weighted-Avg Exercise Price |  |  | Shares |  |  | Weighted-Avg Exercise Price |
$ 8.38 - $40.00 |  |  | 5.45 |  |  |  | 4,121,224 |  |  | $ | 27.17 |  |  |  | 3,124,581 |  |  | $ | 27.53 |
$ 40.01 - $65.00 |  |  | 7.48 |  |  |  | 4,104,562 |  |  |  | 49.50 |  |  |  | 1,919,040 |  |  |  | 55.72 |
$ 65.01 - $79.80 |  |  | 9.11 |  |  |  | 2,255,964 |  |  |  | 79.60 |  |  |  | 30,344 |  |  |  | 73.53 |
Total |  |  | 7.03 |  |  |  | 10,481,750 |  |  | $ | 47.20 |  |  |  | 5,073,965 |  |  | $ | 38.47 |
Assumption used in determination of fair value of share based payment awards |
|  | Years Ended December 31, |
|  | 2011 |  |  | 2010 |  |  | 2009 |
Valuation Assumptions: |  |  |  |  |  |  |  |  |  |  |  |
Expected volatility |  |  | 53.2 | % |  |  | 55.0 | % |  |  | 63.5 | %
Risk-free interest rate |  |  | 2.1 | % |  |  | 2.3 | % |  |  | 1.8 | %
Expected dividends |  | $ | 0.44 |  |  | $ | 0.40 |  |  | $ | — |
Expected term (in years) |  |  | 3.1 |  |  |  | 3.2 |  |  |  | 3.4 |
Summary of Information and changes in stock options with regard to stock option plans |
|  | Shares |  |  | Weighted- Average Exercise Price |  |  | Remaining Contractual Term (years) |  |  | Aggregate Intrinsic Value |
Outstanding at December 31, 2010 |  |  | 11,039,544 |  |  | $ | 38.01 |  |  |  |  |  |  |  |  |
Granted |  |  | 2,277,946 |  |  | $ | 79.68 |  |  |  |  |  |  |  |  |
Exercised |  |  | (2,594,566 | ) |  | $ | 36.84 |  |  |  |  |  |  |  |  |
Cancelled |  |  | (241,174 | ) |  | $ | 40.20 |  |  |  |  |  |  |  |  |
Outstanding at December 31, 2011 |  |  | 10,481,750 |  |  | $ | 47.20 |  |  |  | 7.03 |  |  | $ | 217,950,989 |
Vested or expected to vest |  |  | 10,298,319 |  |  | $ | 47.20 |  |  |  | 7.03 |  |  | $ | 214,136,846 |
Exercisable at December 31, 2011 |  |  | 5,073,965 |  |  | $ | 38.47 |  |  |  | 5.61 |  |  | $ | 149,787,693 |
Summary of information regarding outstanding restricted shares |
Restricted Shares |  | Units |  |  | Weighted-Average Grant Date Fair Value |
Nonvested at December 31, 2008 |  |  | 1,460,496 |  |  | $ | 47.34 |
Granted |  |  | 762,692 |  |  | $ | 26.02 |
Vested |  |  | (7,322 | ) |  | $ | 36.05 |
Forfeited |  |  | (34,622 | ) |  | $ | 41.52 |
Nonvested at December 31, 2009 |  |  | 2,181,244 |  |  | $ | 40.51 |
Granted |  |  | 558,531 |  |  | $ | 43.99 |
Vested |  |  | (921,454 | ) |  | $ | 43.28 |
Forfeited |  |  | (52,484 | ) |  | $ | 35.11 |
Nonvested at December 31, 2010 |  |  | 1,765,837 |  |  | $ | 42.15 |
Granted |  |  | 374,425 |  |  | $ | 79.53 |
Vested |  |  | (496,642 | ) |  | $ | 64.22 |
Forfeited |  |  | (37,573 | ) |  | $ | 44.02 |
Nonvested at December 31, 2011 |  |  | 1,606,047 |  |  | $ | 44.21 |

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