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Share-Based Compensation - Additional Information (Detail) (USD $)
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12 Months Ended | 1 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended | |||||||||||||||
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Dec. 31, 2012
Plans
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Dec. 31, 2011
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Dec. 31, 2010
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Mar. 31, 2008
Chairman and Chief Executive Officer [Member]
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Dec. 31, 2012
Incentive Plan Stock Units Other [Member]
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Dec. 31, 2012
Incentive Plan Stock Units [Member]
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Dec. 31, 2012
Incentive Plan Stock Units [Member]
Incentive Plan Stock Units Other [Member]
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Dec. 31, 2012
SARs [Member]
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Dec. 31, 2012
SARs [Member]
Incentive Plan Stock Units Other [Member]
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Dec. 31, 2012
Stock options [Member]
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Mar. 31, 2008
Stock units [Member]
Chairman and Chief Executive Officer [Member]
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Dec. 31, 2012
Stock units [Member]
Independent Director [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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Dec. 31, 2012
Market condition awards [Member]
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Dec. 31, 2011
Market condition awards [Member]
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Dec. 31, 2010
Market condition awards [Member]
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Dec. 31, 2012
Service condition awards [Member]
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Dec. 31, 2011
Service condition awards [Member]
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Dec. 31, 2010
Service condition awards [Member]
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Dec. 31, 2012
Market and performance condition awards [Member]
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Dec. 31, 2011
Market and performance condition awards [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||||||||||||||||||||
| Number of share based compensation plan | 5 | |||||||||||||||||||||
| Common shares authorized under 2005 Stock Incentive Plan | 14,400,000 | |||||||||||||||||||||
| Common shares remain for future issuance under share based compensation plans | 3,100,000 | |||||||||||||||||||||
| Contractual term | 3 years | 10 years | 10 years | |||||||||||||||||||
| Vesting period beginning from the grant date | 5 years | 3 years | 5 years | 3 years | 5 years | 4 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% | ||||||||||||||||||||
| Share-based compensation expense | $ 700,000 | $ 2,900,000 | $ 3,000,000 | $ 22,700,000 | $ 19,200,000 | $ 20,000,000 | $ 4,600,000 | $ 1,400,000 | ||||||||||||||
| Realized income tax benefit for all awards | 9,500,000 | 7,500,000 | 7,400,000 | |||||||||||||||||||
| Unrecognized compensation cost on non-vested stock awards | 41,200,000 | 9,000,000 | ||||||||||||||||||||
| Unrecognized compensation cost on non-vested stock awards, weighted-average period of recognition | 1 year 4 months 24 days | 2 years | ||||||||||||||||||||
| Excess tax benefit | 29,684,000 | 26,241,000 | 9,254,000 | |||||||||||||||||||
| Total intrinsic value of awards exercised for options and SARs | 98,600,000 | 133,800,000 | 63,800,000 | |||||||||||||||||||
| Weighted-average grant date fair value of SARs granted | $ 15.36 | $ 21.23 | $ 9.32 | $ 17.37 | ||||||||||||||||||
| Total vesting date fair value of stock units | $ 24,300,000 | $ 19,800,000 | $ 10,300,000 | |||||||||||||||||||
| Percent of fair market value for which eligible employees can purchase common shares under employee stock purchase plan | 85.00% | |||||||||||||||||||||
| Reserved for issuance under employee stock purchase plan | 2,000,000 | |||||||||||||||||||||
| Future Issuance of employee stock purchase plan | 1,800,000 | |||||||||||||||||||||