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Share-Based Compensation (Details Textual) (USD $)
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12 Months Ended | 1 Months Ended | 12 Months Ended | ||||||||||||||||||
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Dec. 31, 2011
Plans
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Dec. 31, 2010
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Dec. 31, 2009
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Dec. 31, 2011
Stock Appreciation Rights (SARS) [Member]
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Dec. 31, 2011
Stock Options [Member]
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Dec. 31, 2011
Market Condition Awards [Member]
Y
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Dec. 31, 2010
Market Condition Awards [Member]
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Dec. 31, 2009
Market Condition Awards [Member]
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Dec. 31, 2011
Service Condition Awards [Member]
Y
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Dec. 31, 2010
Service Condition Awards [Member]
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Dec. 31, 2009
Service Condition Awards [Member]
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Dec. 31, 2011
Market And Performance Condition Awards [Member]
Y
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Dec. 31, 2011
Incentive Plan Stock Units [Member]
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Mar. 31, 2008
Market Condition 1 [Member]
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Mar. 31, 2008
Market Condition Target 2 [Member]
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Mar. 31, 2008
Chairman and Chief Executive Officer [Member]
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Mar. 31, 2008
Chairman and Chief Executive Officer [Member]
Stock Units [Member]
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Dec. 31, 2011
Independent Director [Member]
Stock Units [Member]
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Dec. 31, 2011
Incentive Plan Stock Units Other [Member]
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Dec. 31, 2011
Incentive Plan Stock Units Other [Member]
Stock Appreciation Rights (SARS) [Member]
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Dec. 31, 2011
Incentive Plan Stock Units Other [Member]
Incentive Plan Stock Units [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||||||||||||||||||
| Company granted SARS subject to service, market and performance | 25,000 | 900,000 | |||||||||||||||||||
| Contractual term | 10 years | 10 years | 3 years | ||||||||||||||||||
| Vesting Period beginning from the grant date | 5 years | 5 years | 4 years | 5 years | 3 years | 3 years | |||||||||||||||
| Stock units vesting rate | 25.00% | ||||||||||||||||||||
| Stock units vesting rate during first three years | 30.00% | ||||||||||||||||||||
| Stock units vesting rate during fourth year | 10.00% | ||||||||||||||||||||
| Granted Stock unit awards to chairman and Chief Executive Officer vesting | Over a four year period at a rate of 30% during each of the first three years and 10% during the Fourth year | ||||||||||||||||||||
| Stock price appreciation rate | 10.00% | 15.00% | |||||||||||||||||||
| Weighted-average grant date fair value of SARs granted | $ 42.82 | $ 21.23 | $ 9.32 | $ 2.04 | $ 17.37 | ||||||||||||||||
| Share-based compensation expense | $ 2,900,000 | $ 3,000,000 | $ 2,700,000 | $ 19,200,000 | $ 20,000,000 | $ 18,400,000 | $ 1,400,000 | ||||||||||||||
| Unrecognized compensation cost on nonvested stock awards | 700,000 | 34,100,000 | 11,700,000 | ||||||||||||||||||
| Unrecognized compensation cost on nonvested stock awards, weighted-average period of recognition | 0.2 | 1.5 | 3.0 | ||||||||||||||||||
| Outstanding market and performance condition SARs | 717,600 | 1,160,500 | 1,500,000 | 1,500,000 | 900,000 | ||||||||||||||||
| Total intrinsic value of awards exercised for options and SARs | 133,800,000 | 63,800,000 | 16,400,000 | ||||||||||||||||||
| Percent of fair market value for which eligible employees can purchase common shares under employee stock purchase plan | 85.00% | ||||||||||||||||||||
| Share-Based Compensation (Textual) [Abstract] | |||||||||||||||||||||
| Number of share based compensation plan | 5 | ||||||||||||||||||||
| Common shares remain for future issuance under share based compensation plans | 5,100,000 | ||||||||||||||||||||
| Common shares authorized under 2005 Stock Incentive Plan | 14,400,000 | ||||||||||||||||||||
| Realized Income tax benefit for all awards | 7,500,000 | 7,400,000 | 7,900,000 | ||||||||||||||||||
| Excess tax benefit | 27,450,000 | 8,045,000 | 3,587,000 | ||||||||||||||||||
| Total vesting date fair value of stock units | $ 19,800,000 | $ 10,300,000 | $ 4,300,000 | ||||||||||||||||||
| Reserved for issuance under employee stock purchase plan | 2,000,000 | ||||||||||||||||||||
| Future Issuance of employee stock purchase plan | 1,900,000 | ||||||||||||||||||||