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Fair Value Measurements Text Tag (Details) (USD $) | Jun. 30, 2012
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Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 | $ 0.001

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- Definition Level 3 assets percent of total assets + References No definition available. + Details
Name: | carv_Level3AssetsPercentOfTotalAssets
Namespace Prefix: | carv_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration