Stock Options Outstanding and Vested and Exercisable (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number of Options Outstanding	4,249,168	3,708,773
Outstanding	6 years 7 months 6 days
Outstanding	$ 14.77	$ 9.43
Options Vested, Number of Options Vested	2,503,676
Options Vested, Weighted Average Exercise Price Per Share	$ 9.67
$1.00 - $5.10
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$ 1.00
Exercise Prices, Upper Limit	$ 5.10
Options Outstanding, Number of Options Outstanding	945,481
Outstanding	2 years 9 months 18 days
Outstanding	$ 4.21
Options Vested, Number of Options Vested	945,481
Options Vested, Weighted Average Exercise Price Per Share	$ 4.21
$5.30 - $9.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$ 5.30
Exercise Prices, Upper Limit	$ 9.00
Options Outstanding, Number of Options Outstanding	1,068,191
Outstanding	6 years
Outstanding	$ 8.07
Options Vested, Number of Options Vested	927,581
Options Vested, Weighted Average Exercise Price Per Share	$ 8.21
$9.50 - $23.85
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$ 9.50
Exercise Prices, Upper Limit	$ 23.85
Options Outstanding, Number of Options Outstanding	976,963
Outstanding	8 years 2 months 12 days
Outstanding	$ 17.61
Options Vested, Number of Options Vested	406,830
Options Vested, Weighted Average Exercise Price Per Share	$ 16.81
$24.39 - $26.67
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$ 24.39
Exercise Prices, Upper Limit	$ 26.67
Options Outstanding, Number of Options Outstanding	861,050
Outstanding	8 years 7 months 6 days
Outstanding	$ 25.13
Options Vested, Number of Options Vested	178,702
Options Vested, Weighted Average Exercise Price Per Share	$ 25.04
$26.75 - $29.19
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$ 26.75
Exercise Prices, Upper Limit	$ 29.19
Options Outstanding, Number of Options Outstanding	397,483
Outstanding	9 years 6 months
Outstanding	$ 28.42
Options Vested, Number of Options Vested	45,082
Options Vested, Weighted Average Exercise Price Per Share	$ 29.02

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- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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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

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

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Number of options vested.

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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

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-Publisher FASB

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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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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