Line of Credit - Additional Information (Detail)	1 Months Ended	6 Months Ended
Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Line of Credit Facility [Line Items]
Loan covenants requirements		The loan covenants require the Company to (i) maintain a current assets to liabilities ratio of at least 1.25:1, (ii) maintain a current debt to tangible net worth ratio of not greater than 1.25:1 and (iii) have positive net income.
Current assets to liabilities ratio	125.00%	125.00%
Current debt to tangible net worth ratio	125.00%	125.00%
Letters of credit in aggregate amount	$ 4,500,000	$ 4,500,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility with borrowing capacity	$ 10,000,000	$ 10,000,000
Interest rate above one month LIBOR rate	1.00%
Fluctuating rate determined by financial institution		fluctuating rate determined by the financial institution to be 1.00% above the daily one-month LIBOR rate.
Outstanding revolving loans	$ 0	$ 0
Renewed credit agreement expiration period		2018-09
Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.00%

Interest rate above one month LIBOR rate.

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Line of credit expiration period.

+ References

No definition available.

+ Details

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Namespace Prefix:	crvl_
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Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility current assets to liabilities ratio.

+ References

No definition available.

+ Details

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Namespace Prefix:	crvl_
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Period Type:	instant

- Definition

Line of credit facility current debt to net worth ratio.

+ References

No definition available.

+ Details

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Namespace Prefix:	crvl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the conditions for borrowing under the credit facility including the nature of any restrictions.

+ References

+ Details

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Data Type:	xbrli:stringItemType
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
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Period Type:

- Details

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