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