Stock-based compensation (Details) (USD $)	6 Months Ended
Jun. 30, 2012
Outstanding-Options	378,394
Granted-Options	10,033
Exercised-Options	(151)
Forfeited-Options	(67,365)
Outstanding-Options	320,911
Exercisable-Options	204,337
Outstanding-Weighted Average Exercise Price	$ 14.91
Granted-Weighted Average Exercise Price	$ 6.46
Exercised-Weighted Average Exercise Price	$ 6.46
Forfeited-Weighted Average Exercise Price	$ 20.62
Outstanding-Weighted Average Exercise Price	$ 13.45
Exercisable-Weighted Average Exercise Price	$ 15.10
Outstanding-Weighted Average Remaining Contractual Life (Years)	2 years 5 months 12 days
Exercisable-Weighted Average Remaining Contractual Life (Years)	1 year 7 months 10 days
Outstanding-Aggregate Intrinsic Value	$ 52,552
Exercisable-Aggregate Intrinsic Value	$ 52,552

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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For presentations that combine terminations, 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 or that expired.

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Weighted average price of options that were either forfeited or expired.

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

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

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