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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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- Definition

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

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-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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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.

+ References

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

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- Definition

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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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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-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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Share-Based Compensation - Schedule of Information with Respect to Outstanding and Exercisable Stock Options (Detail) (USD $)	12 Months Ended
	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, Number of Options Outstanding	2,591,887	3,353,462	3,574,614	3,213,102
Options Outstanding, Weighted Average Exercise Price	$ 25.96	$ 27.79	$ 28.29	$ 28.30
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	5 years 3 months 11 days
Options Exercisable, Number Exercisable	1,936,936
Options Exercisable, Weighted Average Exercise Price	$ 30.24
Range Of Exercise Prices $2.62 - $6.62 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 2.62
Range of Exercise Prices, Maximum	$ 6.62
Options Outstanding, Number of Options Outstanding	135,325
Options Outstanding, Weighted Average Exercise Price	$ 5.85
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	9 years 5 months 9 days
Options Exercisable, Number Exercisable	24,000
Options Exercisable, Weighted Average Exercise Price	$ 6.51
Range Of Exercise Prices $8.63 - $8.63 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 8.63
Range of Exercise Prices, Maximum	$ 8.63
Options Outstanding, Number of Options Outstanding	326,344
Options Outstanding, Weighted Average Exercise Price	$ 8.63
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	9 years 1 month 28 days
Range Of Exercise Prices $13.32 - $18.64 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 13.32
Range of Exercise Prices, Maximum	$ 18.64
Options Outstanding, Number of Options Outstanding	309,500
Options Outstanding, Weighted Average Exercise Price	$ 16.42
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	5 years 11 days
Options Exercisable, Number Exercisable	309,500
Options Exercisable, Weighted Average Exercise Price	$ 16.42
Range Of Exercise Prices $19.38 - $22.04 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 19.38
Range of Exercise Prices, Maximum	$ 22.04
Options Outstanding, Number of Options Outstanding	317,314
Options Outstanding, Weighted Average Exercise Price	$ 21.85
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	6 years 7 months 2 days
Options Exercisable, Number Exercisable	232,831
Options Exercisable, Weighted Average Exercise Price	$ 21.87
Range Of Exercise Prices $22.13 - $29.02 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 22.13
Range of Exercise Prices, Maximum	$ 29.02
Options Outstanding, Number of Options Outstanding	335,128
Options Outstanding, Weighted Average Exercise Price	$ 25.72
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	6 years 9 months 22 days
Options Exercisable, Number Exercisable	202,329
Options Exercisable, Weighted Average Exercise Price	$ 25.74
Range Of Exercise Prices $29.35 - $30.67 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 29.35
Range of Exercise Prices, Maximum	$ 30.67
Options Outstanding, Number of Options Outstanding	380,250
Options Outstanding, Weighted Average Exercise Price	$ 30.00
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	3 years 8 months 12 days
Options Exercisable, Number Exercisable	380,250
Options Exercisable, Weighted Average Exercise Price	$ 30.00
Range Of Exercise Prices $30.80 - $33.96 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 30.80
Range of Exercise Prices, Maximum	$ 33.96
Options Outstanding, Number of Options Outstanding	307,750
Options Outstanding, Weighted Average Exercise Price	$ 32.45
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	3 years 8 months 16 days
Options Exercisable, Number Exercisable	307,750
Options Exercisable, Weighted Average Exercise Price	$ 32.45
Range Of Exercise Prices $34.70 - $35.29 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 34.70
Range of Exercise Prices, Maximum	$ 35.29
Options Outstanding, Number of Options Outstanding	281,801
Options Outstanding, Weighted Average Exercise Price	$ 34.76
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	2 years 4 months 13 days
Options Exercisable, Number Exercisable	281,801
Options Exercisable, Weighted Average Exercise Price	$ 34.76
Range Of Exercise Prices $35.73 - $64.12 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 35.73
Range of Exercise Prices, Maximum	$ 64.12
Options Outstanding, Number of Options Outstanding	195,350
Options Outstanding, Weighted Average Exercise Price	$ 59.54
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	1 year 4 months 13 days
Options Exercisable, Number Exercisable	195,350
Options Exercisable, Weighted Average Exercise Price	$ 59.54
Range Of Exercise Prices $68.24 - $68.24 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 68.24
Range of Exercise Prices, Maximum	$ 68.24
Options Outstanding, Number of Options Outstanding	3,125
Options Outstanding, Weighted Average Exercise Price	$ 68.24
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	1 year 5 months 5 days
Options Exercisable, Number Exercisable	3,125
Options Exercisable, Weighted Average Exercise Price	$ 68.24