Share-Based Compensation - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding as of December 31, 2012, Options	2,592
Granted, Options	890
Exercised, Options
Forfeited, Options	(69)
Cancelled, Options	(33)
Outstanding as of March 31, 2013, Options	3,380
Exercisable as of March 31, 2013, Options	2,111
Outstanding as of December 31, 2012, Weighted Average Exercise Price	$ 25.96
Granted, Weighted Average Exercise Price	$ 2.72
Exercised, Weighted Average Exercise Price
Forfeited, Weighted Average Exercise Price	$ 6.21
Cancelled, Weighted Average Exercise Price	$ 34.21
Outstanding as of March 31, 2013, Weighted Average Exercise Price	$ 20.16
Exercisable as of March 31, 2013, Weighted Average Exercise Price	$ 28.66

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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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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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

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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.

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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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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 of the plan that expired.

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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 price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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

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