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

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
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

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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

- 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

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

+ Details

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

- Definition

The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

+ Details

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

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

+ Details

Name:	us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt instrument issuance price, percentage of par value.

+ References

No definition available.

+ Details

Name:	xec_DebtInstrumentIssuancePricePercentageOfParValue
Namespace Prefix:	xec_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the redemption price for each $1000 of the debt instrument's principal amount.

+ References

No definition available.

+ Details

Name:	xec_DebtInstrumentRedemptionPricePerPrincipalAmount
Namespace Prefix:	xec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the principal amount (as the denominator) used to state the redemption price of the debt instrument.

+ References

No definition available.

+ Details

Name:	xec_DebtInstrumentRedemptionPricePrincipalAmountDenominator
Namespace Prefix:	xec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the tender price for each $1000 of the debt instrument's principal amount.

+ References

No definition available.

+ Details

Name:	xec_DebtInstrumentTenderPricePerPrincipalAmount
Namespace Prefix:	xec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the principal amount (as the denominator) used to state the tender price of the debt instrument.

+ References

No definition available.

+ Details

Name:	xec_DebtInstrumentTenderPricePrincipalAmountDenominator
Namespace Prefix:	xec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt To Capital Ratio

+ References

No definition available.

+ Details

Name:	xec_DebtToCapitalRatio
Namespace Prefix:	xec_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the estimated offering cost.

+ References

No definition available.

+ Details

Name:	xec_EstimatedOfferingCosts
Namespace Prefix:	xec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Settled Tendered Notes Including Accrued Interest

+ References

No definition available.

+ Details

Name:	xec_SettledTenderedNotesIncludingAccruedInterest
Namespace Prefix:	xec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=xec_Notes4375Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=xec_Notes5.875PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=xec_SeniorUnsecuredNotes3.90PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LONG-TERM DEBT (Details) - USD ($)		3 Months Ended
LONG-TERM DEBT (Details) - USD ($)	Apr. 10, 2017	Mar. 31, 2017	May 12, 2017	Apr. 12, 2017	Apr. 07, 2017	Apr. 03, 2017	Dec. 31, 2016
Debt Instrument
Unamortized debt issuance costs		$ 11,500,000					$ 12,061,000
Long-term Debt, Excluding Current Maturities		1,488,500,000					1,487,939,000
Revolving Credit Facility [Member]
Debt Instrument
Unamortized debt issuance costs		4,200,000					4,500,000
Borrowings outstanding		0					0
Credit facility amount		1,000,000,000
Credit facility, increase amount option		1,250,000,000
Letters of credit outstanding under the credit facility		2,500,000
Unused borrowing availability		$ 997,500,000
Debt-to-Capital ratio		65.00%
Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument
Commitment fee percentage		0.125%
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument
Commitment fee percentage		0.35%
Senior Notes 4.375% [Member]
Debt Instrument
Unamortized debt issuance costs		$ 6,119,000					$ 6,370,000
Interest rate (as a percent)		4.375%					4.375%
Effective rate		4.50%
Long-term Debt, Excluding Current Maturities		$ 743,881,000					$ 743,630,000
Senior Notes 5.875% [Member]
Debt Instrument
Unamortized debt issuance costs		$ 5,381,000					$ 5,691,000
Interest rate (as a percent)		5.875%					5.875%
Effective rate		6.04%
Long-term Debt, Excluding Current Maturities		$ 744,619,000					$ 744,309,000
Senior Notes 5.875% [Member] \| Subsequent Events
Debt Instrument
Interest rate (as a percent)				5.875%		5.875%
Settled tendered notes including accrued interest	$ 268,100,000
Principal amount					$ 253,500,000
Tender price of debt instrument for each $1000 principal amount						$ 1,031.67
Principal amount used for ratio of debt instrument tender price						$ 1,000
Redemption price of debt instrument for each $1000 principal amount			$ 1,029.38
Principal amount used for ratio of debt instrument redemption price			$ 1,000
Senior Unsecured Notes 3.90% [Member] \| Subsequent Events
Debt Instrument
Interest rate (as a percent)	3.90%
Effective rate	3.93%
Principal amount	$ 750,000,000
Debt instrument issuance price, at par percentage	99.748%
Proceeds from Issuance of Unsecured Debt	$ 743,200,000
Estimated offering cost	$ 1,500,000
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument
Interest rate margin (as a percent)		1.125%
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument
Interest rate margin (as a percent)		2.00%
Base Rate [Member] \| Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument
Interest rate margin (as a percent)		0.125%
Base Rate [Member] \| Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument
Interest rate margin (as a percent)		1.00%