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Quarterly Financial Data Quarterly Financial Data Text Tags (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2013 | Mar. 31, 2014
Quarterly Financial Data [Abstract] |  |
Pension plan adjustment | $ 432 | $ 716

X
- Definition Pension plan adjustment + References No definition available. + Details
Name: | carv_Pensionplanadjustment
Namespace Prefix: | carv_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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