The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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-Name Accounting Standards Codification

-Topic 718

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-SubTopic 10

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- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Summary of Stock Option Outstanding (Detail) (USD $)	12 Months Ended
Summary of Stock Option Outstanding (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding	227,743	272,201	323,948	324,720
Options Outstanding, Weighted-Average Remaining Contractual Life	3 years 6 months
Options Outstanding, Weighted-Average Exercise Price	$ 27.81	$ 25.98	$ 25.06	$ 28.47
Options Exercisable	202,743	222,201	248,948
Options Exercisable, Weighted-Average Exercise Price	$ 30.05	$ 29.67	$ 29.72
$ 9.61 - $ 9.61
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 9.61
Range of Exercise Price, Upper Limit	$ 9.61
Options Outstanding	25,000
Options Outstanding, Weighted-Average Remaining Contractual Life	7 years 1 month 6 days
Options Outstanding, Weighted-Average Exercise Price	$ 9.61
$ 23.77 - $ 27.96
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 23.77
Range of Exercise Price, Upper Limit	$ 27.96
Options Outstanding	79,917
Options Outstanding, Weighted-Average Remaining Contractual Life	1 year 10 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 26.49
Options Exercisable	79,917
Options Exercisable, Weighted-Average Exercise Price	$ 26.49
$ 28.80 $ 29.06
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 28.80
Range of Exercise Price, Upper Limit	$ 29.06
Options Outstanding	49,806
Options Outstanding, Weighted-Average Remaining Contractual Life	3 years
Options Outstanding, Weighted-Average Exercise Price	$ 29.01
Options Exercisable	49,806
Options Exercisable, Weighted-Average Exercise Price	$ 29.01
$ 34.30 $ 36.50
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 34.30
Range of Exercise Price, Upper Limit	$ 36.50
Options Outstanding	73,020
Options Outstanding, Weighted-Average Remaining Contractual Life	4 years 2 months 12 days
Options Outstanding, Weighted-Average Exercise Price	$ 34.66
Options Exercisable	73,020
Options Exercisable, Weighted-Average Exercise Price	$ 34.66