v2.4.1.9

Stock Options Outstanding Under Equity Incentive Plans (Detail) (USD $) | 12 Months Ended |
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Outstanding Options | 101,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 279,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 433,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Weighted Average Exercise Price | $ 5.31 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 3.31 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 3.60 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Weighted Average Remaining Contractual Life (Years) | 4 years | 2 years 6 months |
Options Exercisable | 93,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber |  |
Weighted Average Exercise Price | $ 5.48 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice |  |
Previously Approved Plans | $1.80 - $4.25 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Range of exercise prices, lower limit | $ 1.80 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeOneMember |  |
Range of exercise prices, upper limit | $ 4.25 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeOneMember |  |
Outstanding Options | 46,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeOneMember |  |
Weighted Average Exercise Price | $ 3.14 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeOneMember |  |
Weighted Average Remaining Contractual Life (Years) | 7 years 2 months 12 days |  |
Options Exercisable | 38,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeOneMember |  |
Weighted Average Exercise Price | $ 3.11 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeOneMember |  |
Previously Approved Plans | $4.90 - $9.80 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Range of exercise prices, lower limit | $ 4.90 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeTwoMember |  |
Range of exercise prices, upper limit | $ 9.80 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeTwoMember |  |
Outstanding Options | 55,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeTwoMember |  |
Weighted Average Exercise Price | $ 7.12 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeTwoMember |  |
Weighted Average Remaining Contractual Life (Years) | 1 year 3 months 18 days |  |
Options Exercisable | 55,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeTwoMember |  |
Weighted Average Exercise Price | $ 7.12 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeTwoMember |  |
Previously Approved Plans | $1.80 - $9.80 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Range of exercise prices, lower limit | $ 1.80 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeThreeMember |  |
Range of exercise prices, upper limit | $ 9.80 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeThreeMember |  |
Outstanding Options | 101,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeThreeMember |  |
Weighted Average Exercise Price | $ 5.31 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeThreeMember |  |
Weighted Average Remaining Contractual Life (Years) | 4 years |  |
Options Exercisable | 93,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeThreeMember |  |
Weighted Average Exercise Price | $ 5.48 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice / crv_IncentiveCompensationPlansEmployeesAxis = crv_EquityIncentivePlanMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = crv_RangeThreeMember |  |

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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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