EMPLOYEE BENEFIT PLANS (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Contribution and Deferred Compensation Plans Disclosures [Line Items]
Number of defined contribution retirement plans sponsored	1
401 (k) Retirement Savings Plan [Member]
Defined Contribution and Deferred Compensation Plans Disclosures [Line Items]
Maximum participant compensation deferral amount (in hundredths)	75.00%
Entity's matching contribution, first range (in hundredths)	100.00%
Participant's eligible contribution, first range (in hundredths)	3.00%
Entity's matching contribution, second range (in hundredths)	50.00%
Participant's eligible contribution, second range (in hundredths)	3.00%
Cost of employee benefit plan	$ 31.2	$ 29.7	$ 27.4
401 (k) Restoration and Deferred Compensation Plan [Member]
Defined Contribution and Deferred Compensation Plans Disclosures [Line Items]
Maximum participant compensation deferral amount (in hundredths)	75.00%
Entity's matching contribution, first range (in hundredths)	100.00%
Participant's eligible contribution, first range (in hundredths)	3.00%
Entity's matching contribution, second range (in hundredths)	50.00%
Participant's eligible contribution, second range (in hundredths)	3.00%
Cost of employee benefit plan	$ 2.2	$ 1.4	$ 0.4
Maximum participant bonus deferral amount (in hundredths)	100.00%
Vesting period (in years)	2 years

Name:	cvh_DefinedContributionAndDeferredCompensationPlansDisclosuresLineItems
Namespace Prefix:	cvh_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The percentage of entity's matching contribution on the participant's first range of eligible contribution under an existing employee benefit plan.

+ References

No definition available.

+ Details

Name:	cvh_EntitysMatchingContributionFirstRange
Namespace Prefix:	cvh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of entity's matching contribution on the participant's second range of eligible contribution under an existing employee benefit plan.

+ References

No definition available.

+ Details

Name:	cvh_EntitysMatchingContributionSecondRange
Namespace Prefix:	cvh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of participant's bonus awarded that may be deferred under an existing employee benefit plan.

+ References

No definition available.

+ Details

Name:	cvh_MaximumParticipantBonusDeferralAmount
Namespace Prefix:	cvh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of participant's eligible compensation that may be deferred under an existing employee benefit plan, limited by the maximum compensation deferral amount permitted by applicable law.

+ References

No definition available.

+ Details

Name:	cvh_MaximumParticipantCompensationDeferralAmount
Namespace Prefix:	cvh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of defined contribution retirement plans qualifying under the Internal Revenue Code Section 401 (k) sponsored by the entity.

+ References

No definition available.

+ Details

Name:	cvh_NumberOfDefinedContributionRetirementPlansSponsored
Namespace Prefix:	cvh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of participant's first range of eligible contribution matched by the entity under an existing employee benefit plan.

+ References

No definition available.

+ Details

Name:	cvh_ParticipantsEligibleContributionFirstRange
Namespace Prefix:	cvh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of participant's second range of eligible contribution matched by the entity under an existing employee benefit plan.

+ References

No definition available.

+ Details

Name:	cvh_ParticipantsEligibleContributionSecondRange
Namespace Prefix:	cvh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The vesting period for the Company's matching contributions in Restore Plan.

+ References

No definition available.

+ Details

Name:	cvh_VestingPeriod
Namespace Prefix:	cvh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration