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Capital Stock (Detail) (USD $)
In Millions, except Share data, unless otherwise specified |
1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 01, 2012
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Apr. 27, 2012
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Mar. 13, 2012
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Mar. 01, 2012
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Feb. 15, 2012
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Dec. 01, 2011
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Nov. 18, 2011
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Sep. 01, 2011
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Aug. 15, 2011
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Jul. 12, 2011
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Jun. 13, 2011
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Jun. 01, 2011
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Apr. 29, 2011
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Mar. 01, 2011
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Feb. 15, 2011
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Oct. 31, 2012
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Oct. 15, 2012
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Dec. 31, 2011
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Sep. 30, 2011
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Jun. 30, 2011
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Sep. 30, 2012
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Sep. 30, 2011
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Aug. 31, 2012
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May 25, 2011
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| Dividend payable, per share | $ 0.625 | $ 0.280 | $ 0.280 | $ 0.28 | $ 0.140 | $ 0.14 | $ 0.625 | |||||||||||||||||
| Common share dividends date paid | Jun. 01, 2012 | Mar. 01, 2012 | Dec. 01, 2011 | Sep. 01, 2011 | Jun. 01, 2011 | Mar. 01, 2011 | Aug. 31, 2012 | |||||||||||||||||
| Common share dividends date of record | Apr. 27, 2012 | Feb. 15, 2012 | Nov. 18, 2011 | Aug. 15, 2011 | Apr. 29, 2011 | Feb. 15, 2011 | Aug. 15, 2012 | |||||||||||||||||
| Percentage increase in dividends payable | 123.00% | 100.00% | ||||||||||||||||||||||
| Share repurchase plan, number of common shares authorized for repurchase | 4,000,000 | |||||||||||||||||||||||
| Shares repurchased (in shares) | 1,000,000 | 3,000,000 | ||||||||||||||||||||||
| Share buyback | $ 222.0 | $ 221.9 | ||||||||||||||||||||||
| Shares repurchased, average price (in usd per share) | $ 74 | |||||||||||||||||||||||
| Issuance of common shares, public offering (in shares) | 10,350,000 | |||||||||||||||||||||||
| Common shares, issued (in shares) | 149,195,469 | 149,195,469 | ||||||||||||||||||||||
| Net proceeds from issuance of common shares | $ 853.7 | $ 0 | $ 853.7 | |||||||||||||||||||||
| Closing price per share (in usd per share) | $ 85.63 | |||||||||||||||||||||||
| Common shares, authorized (in shares) | 400,000,000 | 400,000,000 | 224,000,000 | |||||||||||||||||||||
| Total shares authorized (in shares) | 231,000,000 | |||||||||||||||||||||||
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Maximum [Member]
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| Common shares, authorized (in shares) | 400,000,000 | |||||||||||||||||||||||
| Total shares authorized (in shares) | 407,000,000 | |||||||||||||||||||||||
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Common Shares [Member]
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| Common shares, issued (in shares) | 9,000,000 | |||||||||||||||||||||||
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Over Allotment Option [Member]
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| Common shares, issued (in shares) | 1,350,000 | |||||||||||||||||||||||
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Preferred Class A [Member]
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| Preferred stock, shares authorized (in shares) | 3,000,000 | |||||||||||||||||||||||
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Preferred Class B [Member]
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| Preferred stock, shares authorized (in shares) | 4,000,000 | |||||||||||||||||||||||