v2.4.1.9

Valuation and Qualifying Accounts (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 278,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		$ 311,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		$ 387,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Adjustments	88,000us-gaap_ValuationAllowancesAndReservesAdjustments / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		115,000us-gaap_ValuationAllowancesAndReservesAdjustments / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		23,000us-gaap_ValuationAllowancesAndReservesAdjustments / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Deductions	(141,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		(148,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		(99,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Balance at End of Period	225,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		278,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember		311,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Allowance for Obsolete or Slow-Moving Inventory
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	1,454,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		1,439,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		1,401,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember
Adjustments	176,000us-gaap_ValuationAllowancesAndReservesAdjustments / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		251,000us-gaap_ValuationAllowancesAndReservesAdjustments / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		224,000us-gaap_ValuationAllowancesAndReservesAdjustments / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember
Deductions	(235,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		(236,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		(186,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember
Balance at End of Period	1,395,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		1,454,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember		1,439,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = crv_AllowanceForObsoleteOrSlowMovingInventoryMember
Valuation Allowance of Deferred Tax Assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	1,369,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember		1,376,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember		1,213,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Additions					163,000crv_ValuationAllowancesAndReservesAdditions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Deductions	(15,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember	[1]	(7,000)us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember	[1]
Balance at End of Period	$ 1,354,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember		$ 1,369,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember		$ 1,376,000us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
[1] Net operating loss carryforwards used or expired.

X

- Definition

Valuation Allowances And Reserves Additions

+ References

No definition available.

+ Details

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Period Type:	duration

X

- Definition

Total of the adjustments in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

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- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

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X

- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

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