Option Activity under Stock Plans (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015
Number of Options Outstanding
Beginning balance	1,820
Options granted	619
Options exercised	(2)
Ending balance	2,313
Vested and expected to vest at end of period	2,313
Exercisable at end of period	1,126
Weighted-Average Price Per Share
Beginning balance	$ 27.48
Options granted	$ 16.30
Options exercised	$ 10.22
Ending balance	$ 24.06
Vested and expected to vest at end of period	$ 24.06
Exercisable at end of period	$ 30.20
Weighted Average Remaining Contractual Life (In years)
Balance at March 31, 2015	6 years 11 months 9 days
Outstanding options vested and expected to vest at end of period	6 years 11 months 9 days
Options exercisable at end of period	4 years 6 months 18 days
Aggregate Intrinsic Value
Balance at March 31, 2015	$ 8,276
Outstanding options (vested and expected to vest) at end of period	8,276
Options exercisable at end of period	$ 2,298
Unvested
Number of Options Outstanding
Options cancelled	(54)
Weighted-Average Price Per Share
Options cancelled	$ 17.88
Vested
Number of Options Outstanding
Options cancelled	(70)
Weighted-Average Price Per Share
Options cancelled	$ 48.75

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Share based compensation arrangement by share based payment award options and equity instruments other than options nonvested weighted average price.

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

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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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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.

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

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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

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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.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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