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Fair Value Measurements Text Tag (Details) | 6 Months Ended
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Sep. 30, 2015
FAIR VALUE MEASUREMENTS [Abstract] |
Percent of Total Assets Level 3 | 0.03%

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- Definition FAIR VALUE MEASUREMENTS [Abstract] + References No definition available. + Details
Name: | carv_FairValueMeasurementsAbstract
Namespace Prefix: | carv_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Percent of Total Assets Level 3 + References No definition available. + Details
Name: | carv_PercentOfTotalAssetsLevel3
Namespace Prefix: | carv_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration