1. Stock-based Compensation (Details) (USD $)	3 Months Ended
Mar. 31, 2013
Number of Shares
Outstanding options, beginning balance	8,652
Granted	1,465
Exercised	(356)
Outstanding options, ending balance	9,761
Options exercisable	5,449
Outstanding options, beginning balance	$ 1.58
Granted	$ 6.86
Exercised	$ 1.76
Outstanding options, ending balance	$ 2.37
Options exercisable	$ 1.69
Weighted Average Remaining Contractual Term
Outstanding options, ending balance	6 years 6 months 22 days
Options exercisable	4 years 9 months 22 days

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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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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 can acquire the shares reserved for issuance on stock options awarded.

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

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

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

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