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Stock incentive plans (Details 4) (USD $)
In Thousands, except Per Share data, unless otherwise specified |
12 Months Ended | |||
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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| Number of Options | ||||
| Outstanding at the beginning of the period (in shares) | 4,955us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 5,045us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 6,601us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | |
| Granted (in shares) | 203us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross | 1,351us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross | 1,391us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross | |
| Exercised (in shares) | (458)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised | (461)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised | (1,899)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised | |
| Canceled/forfeited (in shares) | (359)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod | (980)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod | (1,048)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod | |
| Outstanding at the end of the period (in shares) | 4,341us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 4,955us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 5,045us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 6,601us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber |
| Vested, exercisable and expected to vest at the end of the period (in shares) | 4,267us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber | |||
| Exercisable at the end of the period (in shares) | 3,053us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber | |||
| Weighted Average Exercise Price | ||||
| Outstanding at the beginning of the period (in dollars per share) | $ 6.31us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 6.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 5.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | |
| Granted (in dollars per share) | $ 5.99us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice | $ 6.73us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice | $ 8.29us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice | |
| Exercised (in dollars per share) | $ 2.53us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice | $ 1.33us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice | $ 1.36us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice | |
| Canceled/forfeited (in dollars per share) | $ 7.53us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice | $ 10.20us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice | $ 11.85us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice | |
| Outstanding at the end of the period (in dollars per share) | $ 6.60us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 6.31us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 6.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 5.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice |
| Vested and expected to vest at the end of the period (in dollars per share) | $ 6.58us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice | |||
| Exercisable at the end of the period (in dollars per share) | $ 5.83us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice | |||
| Weighted-Average Remaining Contract Life (years) | ||||
| Outstanding | 5 years 9 months 18 days | 6 years 7 months 6 days | 6 years 4 months 24 days | 7 years |
| Vested and expected to vest at the end of the period | 5 years 8 months 12 days | |||
| Exercisable at the end of the period | 4 years 10 months 24 days | |||
| Aggregate Intrinsic Value | ||||
| Outstanding at the beginning of the period | $ 9,535us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue | $ 14,742us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue | $ 30,996us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue | |
| Outstanding at the end of the period | 11,017us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue | 9,535us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue | 14,742us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue | 30,996us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue |
| Vested and expected to vest at the end of the period | 10,946us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue | |||
| Exercisable at the end of the period | 10,014us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 | |||
| Cash proceeds from exercise of stock option | 1,158us-gaap_ProceedsFromStockOptionsExercised | 614us-gaap_ProceedsFromStockOptionsExercised | 2,573us-gaap_ProceedsFromStockOptionsExercised | |
| Total intrinsic value of stock options exercised (in dollars) | 2,027us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue | 2,662us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue | 14,901us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue | |
| Tax benefits for the deductions from stock option exercises | $ 55us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions | $ 2,190us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions | ||
| Weighted average grant-date fair value of stock options granted (in dollars per share) | $ 2.92us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue | $ 3.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue | $ 3.59us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue | |
| X | ||||||||||
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- Definition
Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Gross number of share options (or share units) granted during the period. No definition available.
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| X | ||||||||||
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- Definition
The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Number of options outstanding, including both vested and non-vested options. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Weighted average price at which option holders acquired shares when converting their stock options into shares. No definition available.
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| X | ||||||||||
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- Definition
Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated. No definition available.
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| X | ||||||||||
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- Definition
Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options. No definition available.
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| X | ||||||||||
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- Definition
Number of share options (or share units) exercised during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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