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Shareholders' Equity - Additional Information (Detail) (USD $)
Share data in Millions, except Per Share data, unless otherwise specified |
1 Months Ended | 3 Months Ended | 12 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jul. 31, 2012
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Jun. 30, 2012
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May 31, 2012
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Mar. 31, 2012
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Jun. 30, 2011
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Sep. 30, 2010
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Jun. 30, 2010
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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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Jul. 30, 2012
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May 03, 2010
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Apr. 30, 2009
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| Stockholders Equity [Line Items] | |||||||||||||
| Common shares, shares outstanding | 106.9 | 115.8 | 117.8 | ||||||||||
| Preference shares authorized | 7.5 | ||||||||||||
| Preference shares par value | $ 0.002 | ||||||||||||
| Cash dividend per common share | $ 0.30 | $ 0.20 | $ 0.13 | $ 0.10 | |||||||||
| Increase in cash dividends per common share | $ 0.10 | $ 0.07 | $ 0.03 | ||||||||||
| Dividends paid | $ 135,091,000 | $ 85,489,000 | $ 53,740,000 | ||||||||||
| Share repurchase program capacity authorization | 1,000,000,000 | 1,000,000,000 | 300,000,000 | ||||||||||
| Previous expiration date of share repurchase program | Apr. 01, 2011 | ||||||||||||
| Revised expiration date of share repurchase program | Dec. 01, 2014 | ||||||||||||
| Repurchase of common stock | 427,900,000 | 556,727,000 | 321,639,000 | 160,008,000 | |||||||||
| Agreement expiration date | July 27, 2012 | ||||||||||||
| Repurchase of common stock | 3.9 | 5.3 | 11.0 | 5.5 | 5.7 | ||||||||
| Share repurchase program, remaining authorized capacity | 950,000,000 | ||||||||||||
| Shares repurchased through open market purchases, aggregate cost | $ 527,800,000 | $ 298,800,000 | $ 150,100,000 | ||||||||||
| Average cost per share of shares repurchased | $ 47.78 | $ 54.27 | $ 26.13 | ||||||||||