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Stock Incentive Plans - Additional Information (Detail) (USD $)
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12 Months Ended |
1 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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Aug. 31, 2012
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Aggregate pre-tax intrinsic value |
$ 350,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue |
$ 75,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue |
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| Weighted average fair value of options granted |
$ 3.23us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue |
$ 2.77us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue |
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| Stock-based compensation expense |
33,000us-gaap_AllocatedShareBasedCompensationExpense |
24,000us-gaap_AllocatedShareBasedCompensationExpense |
16,000us-gaap_AllocatedShareBasedCompensationExpense |
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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 |
268,985us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
318,660us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
312,501us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Number of restricted shares vested |
103,503us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
105,504us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Intrinsic value of restricted shares vested |
$ 384,500us-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) |
34,793crv_CommonStockCanceledForPaymentOfPayrollTaxesOnVestingOfShareBasedCompensationShares / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Tax withholding obligations |
129,000us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Restricted Stock | Service Contingent |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Stock-based compensation expense |
233,000us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = crv_ServiceBasedOptionsMember |
278,000us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = crv_ServiceBasedOptionsMember |
440,000us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = crv_ServiceBasedOptionsMember |
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| Unrecognized compensation cost |
52,439us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = crv_ServiceBasedOptionsMember |
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| Unvested restricted shares outstanding |
103,494us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = crv_ServiceBasedOptionsMember |
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| Unrecognized compensation costs are expected to be recognized over a weighted average periods (years) |
1 year |
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| Aggregate intrinsic value |
335,321us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = crv_ServiceBasedOptionsMember |
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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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| Stock-based compensation expense |
0us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = us-gaap_PerformanceSharesMember |
0us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = us-gaap_PerformanceSharesMember |
0us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = us-gaap_PerformanceSharesMember |
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| Unrecognized compensation cost |
567,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / crv_StockOptionPlanTypeAxis = us-gaap_PerformanceSharesMember |
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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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| Unrecognized compensation costs are expected to be recognized over a weighted average periods (years) |
9 months 18 days |
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| Aggregate intrinsic value |
536,200us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested / 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 |
| Additional shares authorized for issuance under equity incentive plan |
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17,666us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveMember |
| Shares redistributed and made available for grant |
207,333us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanTwentyTwelveMember |
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| Outstanding shares remained available for future grants |
372,332us-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 |