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Stock Based Compensation - Additional Information (Detail) (USD $)
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3 Months Ended |
1 Months Ended |
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Mar. 31, 2015
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Mar. 31, 2014
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Aug. 31, 2012
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Dec. 31, 2014
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Outstanding options to purchase shares of common stock |
64,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber |
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101,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber |
| Stock-based compensation expense |
$ 143,000us-gaap_ShareBasedCompensation |
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$ 157,000us-gaap_ShareBasedCompensation |
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| Restricted Stock |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Unvested restricted shares outstanding |
165,491us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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268,985us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
| Unrecognized compensation cost |
475,200us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Number of restricted shares vested |
103,494us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
[1] |
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| Intrinsic value of restricted shares vested |
$ 370,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Common stock cancelled in payment of payroll taxes due on vesting of restricted shares under employee stock incentive plans (in shares) |
9,998crv_CommonStockCanceledForPaymentOfPayrollTaxesOnVestingOfShareBasedCompensationShares / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Tax withholding obligations |
35,000us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Unrecognized stock-based compensation expense are expected to be recognized over a weighted average periods (years) |
1 year 4 months 24 days |
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| Restricted shares outstanding expected to vest |
165,491crv_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Aggregate intrinsic value |
571,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Restricted Stock | Service Contingent | Minimum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Vesting period |
3 years |
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| Restricted Stock | Service Contingent | Maximum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Vesting period |
4 years |
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| Restricted Stock | Performance Contingent |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Unvested restricted shares outstanding |
165,491us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = us-gaap_PerformanceSharesMember |
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| Unvested Stock Options |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Unrecognized compensation cost |
$ 0us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = crv_UnvestedStockOptionsMember |
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| 2012 Equity Incentive Plan |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Shares initially authorized for issuance under equity incentive plan |
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300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveMember |
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| Additional shares authorized for issuance under equity incentive plan |
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17,666us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveMember |
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| Shares redistributed and made available for grant |
308,821us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveMember |
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| Outstanding shares remained available for future grants |
419,330us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveMember |
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| Previously Approved Plans |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Shares ceased to be issuable |
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17,666crv_ShareBasedCompensationArrangementByShareBasedPaymentAwardAvailableForGrantCancelledInPeriod / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember |
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| 2012 Plan and Previously Approved Plans |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Outstanding options to purchase shares of common stock |
64,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveAndPreviouslyApprovedPlansMember |
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| 2012 Plan and Previously Approved Plans | Restricted Stock |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Unvested restricted shares outstanding |
165,491us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveAndPreviouslyApprovedPlansMember |
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