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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of options outstanding.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

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

+ References

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- Definition

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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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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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.

+ References

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Information of Option Outstanding and Exercisable (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding and Exercisable, Number	2,091	4,450	5,316	7,289
Options Outstanding and Exercisable, Weighted-Average Remaining Contractual Life	1 year 4 months 24 days
Options Outstanding and Exercisable, Weighted-Average Exercise Price	$ 24.80	$ 21.85	$ 22.04	$ 22.34
Options Outstanding and Exercisable, Aggregate Intrinsic Value	$ 14,671
$13.39 to $22.24
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower	$ 13.39
Range of Exercise Prices, Upper	$ 22.24
Options Outstanding and Exercisable, Number	414
Options Outstanding and Exercisable, Weighted-Average Remaining Contractual Life	7 months 24 days
Options Outstanding and Exercisable, Weighted-Average Exercise Price	$ 19.87
Options Outstanding and Exercisable, Aggregate Intrinsic Value	4,953
$22.85 to $22.85
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower	$ 22.85
Range of Exercise Prices, Upper	$ 22.85
Options Outstanding and Exercisable, Number	535
Options Outstanding and Exercisable, Weighted-Average Remaining Contractual Life	9 months 22 days
Options Outstanding and Exercisable, Weighted-Average Exercise Price	$ 22.85
Options Outstanding and Exercisable, Aggregate Intrinsic Value	4,795
$23.49 to $26.56
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower	$ 23.49
Range of Exercise Prices, Upper	$ 26.56
Options Outstanding and Exercisable, Number	706
Options Outstanding and Exercisable, Weighted-Average Remaining Contractual Life	1 year 10 months 17 days
Options Outstanding and Exercisable, Weighted-Average Exercise Price	$ 26.21
Options Outstanding and Exercisable, Aggregate Intrinsic Value	3,961
$26.61 to $33.89
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower	$ 26.61
Range of Exercise Prices, Upper	$ 33.89
Options Outstanding and Exercisable, Number	436
Options Outstanding and Exercisable, Weighted-Average Remaining Contractual Life	2 years 18 days
Options Outstanding and Exercisable, Weighted-Average Exercise Price	$ 29.61
Options Outstanding and Exercisable, Aggregate Intrinsic Value	$ 962