Fair Value of Employee Stock Options Granted as Determined by Black-Scholes Valuation Model Assumptions (Detail) - Nonqualified Stock Options [Member] |
6 Months Ended | |
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Jun. 30, 2015 |
Jun. 30, 2014 |
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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 | 2.07% | 2.40% |
| Expected volatility | 20.61% | 24.26% |
| Expected dividend yield | 2.63% | 2.56% |
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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 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 Weighted average expected volatility rate of share-based compensation awards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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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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- Details
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