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

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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 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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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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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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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.

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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.

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Stock Based Compensation (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of options outstanding
Options Outstanding, Number Outstanding	565,054	581,888	587,342
Weighted- Average Remaining Contractual Life (Years)	6 years 4 months 24 days
Options Outstanding, Aggregate intrinsic value	$ 463,186
Weighted-average exercise prices	$ 4.29	$ 4.62	$ 4.68
Options Exercisable, Number Exercisable	456,473
Options Exercisable, Aggregate intrinsic value	$ 347,856
Options Exercisable, Weighted- Average Exercise Price	$ 4.76
Range One [Member]
Summary of options outstanding
Range of Exercise Prices, lower limit	$ 1.90
Range of Exercise Prices, upper limit	$ 2.51
Options Outstanding, Number Outstanding	470,371
Weighted- Average Remaining Contractual Life (Years)	7 years
Weighted-average exercise prices	$ 2.39
Options Exercisable, Number Exercisable	361,790
Options Exercisable, Weighted- Average Exercise Price	$ 2.41
Range Two [Member]
Summary of options outstanding
Range of Exercise Prices, upper limit	$ 8.92
Options Outstanding, Number Outstanding	18,877
Weighted- Average Remaining Contractual Life (Years)	4 years 9 months 18 days
Weighted-average exercise prices	$ 8.92
Options Exercisable, Number Exercisable	18,877
Options Exercisable, Weighted- Average Exercise Price	$ 8.92
Range Three [Member]
Summary of options outstanding
Range of Exercise Prices, lower limit	$ 11.36
Range of Exercise Prices, upper limit	$ 14.16
Options Outstanding, Number Outstanding	43,473
Weighted- Average Remaining Contractual Life (Years)	3 years 1 month 6 days
Weighted-average exercise prices	$ 13.69
Options Exercisable, Number Exercisable	43,473
Options Exercisable, Weighted- Average Exercise Price	$ 13.69
Range Four [Member]
Summary of options outstanding
Range of Exercise Prices, lower limit	$ 16.16
Range of Exercise Prices, upper limit	$ 17.17
Options Outstanding, Number Outstanding	32,333
Weighted- Average Remaining Contractual Life (Years)	1 year 8 months 12 days
Weighted-average exercise prices	$ 16.60
Options Exercisable, Number Exercisable	32,333
Options Exercisable, Weighted- Average Exercise Price	$ 16.60