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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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 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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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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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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

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Common Stock and Stock-based Compensation (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of company's stock option activity
Exercise of stock options (in shares)	(20)	(74)	(16)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Number of options outstanding, Weighted Average Exercise Price Per Share, Ending of Period
Number of options, vested and expected to vest, Weighted Average Exercise Price Per Share
Number of options outstanding, exercisable, Weighted Average Exercise Price Per Share
Number of options, outstanding, Weighted Average Remaining Term (Years)	0 years
Number of options, vested and expected to vest, Weighted Average Remaining Term (Years)	0 years
Number of options, Exercisable, Weighted Average Remaining Term (Years)	0 years
Employee Stock Option [Member]
Summary of company's stock option activity
Number of options outstanding, Beginning balance (in shares)	21
Exercise of stock options (in shares)	(20)
Canceled stock options (in shares)	(1)
Number of options outstanding, Ending balance (in shares)	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Number of options outstanding, Weighted average Exercise Price Per Share, Beginning of Period	$ 17.29
Exercised, Weighted average exercise price per share	$ 17.29
Canceled, Weighted average exercise price per share	$ 17.08
Number of options, vested and expected to vest (in shares)	0
Number of options outstanding, exercisable (in shares)	0
Number of options, outstanding, Aggregate Intrinsic Value	$ 0
Number of options, vested and expected to vest, Aggregate Intrinsic Value	0
Number of options, Exercisable, Aggregate Intrinsic Value	$ 0