Roll-forward of Common Stock, Additional Paid-in Capital, and Retained Earnings Accounts (Parenthetical) (Detail) (Retained Earnings, USD $) |
9 Months Ended | |
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Sep. 30, 2011 |
Sep. 30, 2010 |
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Retained Earnings |
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| Stockholders Equity Note [Line Items] | ||
| Dividends, per share | $ 1.56 | $ 1.41 |
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- Definition Stockholders Equity Note [Line Items]
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| X | ||||||||||
- Definition Aggregate dividends paid during the period for each share of common stock outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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