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Fair Value of Employee Stock Options Granted as Determined by Black-Scholes Valuation Model Assumptions (Detail) (Nonqualified Stock Options [Member])
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3 Months Ended | |
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Mar. 31, 2013
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Mar. 31, 2012
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Nonqualified Stock Options [Member]
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| Stockholders Equity Note [Line Items] | ||
| Expected life (in years) | 7 years 6 months | 7 years 6 months |
| Risk-free interest rate | 1.38% | 1.63% |
| Expected volatility | 24.85% | 25.06% |
| Expected dividend yield | 2.75% | 2.77% |
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- Definition
The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The range of expected volatilities used and the weighted-average expected volatility for an entity using a valuation technique with different volatilities during the contractual term. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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