Employee Benefit Plans (Narrative) (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Period of service before an employee is eligible for contribution	1 year
Common stock authorized for issuance but not yet issued for ESPP	246
Common stock authorized and reserved for ESPP	250
ESPP employee contribution, percentage	15.00%
Purchase price percentage of fair market value of stock on last trading date of monthly exercise period	95.00%
Shares issued under ESPP	1	1	1
Fair value of investments in rabbi trust	$ 10,872	$ 19,887
Deferred Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Employer matching contribution, percentage on first 3%	100.00%
Employer matching contribution, percentage on next 2%	50.00%
Percentage of employees' gross pay for which the employer contributes a matching contribution of 100% under the Deferred Plan	3.00%
Percentage of employees' gross pay for which the employer contributes a matching contribution of 50% under the Deferred Plan	2.00%
Total liabilities under Deferred Plan	$ 10,872	19,887
Deferred Compensation Arrangement with Individual, Contributions by Employer	$ 152	199	$ 225
401(k) Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Employer matching contribution, percentage on first 3%	100.00%
Employer matching contribution, percentage on next 2%	50.00%
Percentage of employees' gross pay for which the employer contributes a matching contribution of 100%	3.00%
Percentage of employees' gross pay for which the employer contributes a matching contribution of 50%	2.00%
Period of service before an employee is eligible for contribution	1 year
Company matching contributions	$ 6,090	$ 6,072	$ 5,939

Common stock reserved for issuance under the Company's ESPP.

No definition available.

Name:	cmg_CommonStockAuthorizedAndReservedForIssuanceEspp
Namespace Prefix:	cmg_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Common stock authorized for issuance but not yet issued for ESPP

+ References

No definition available.

+ Details

Name:	cmg_CommonStockAuthorizedForIssuanceButNotYetIssuedForEspp
Namespace Prefix:	cmg_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Deferred Compensation Arrangement With Individual Employer Contribution Percentage On First 3 Percent

+ References

No definition available.

+ Details

Name:	cmg_DeferredCompensationArrangementWithIndividualEmployerContributionPercentageOnFirst3Percent
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Deferred Compensation Arrangement With Individual Employer Contribution Percentage On Next 2 Percent

+ References

No definition available.

+ Details

Name:	cmg_DeferredCompensationArrangementWithIndividualEmployerContributionPercentageOnNext2Percent
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Deferred compensation arrangement with individual, employer matching contribution of 100 percent

+ References

No definition available.

+ Details

Name:	cmg_DeferredCompensationArrangementWithIndividualEmployerMatchingContributionOf100Percent
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Deferred compensation arrangement with individual, employer matching contribution of 50 percent

+ References

No definition available.

+ Details

Name:	cmg_DeferredCompensationArrangementWithIndividualEmployerMatchingContributionOf50Percent
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay, at Which Employer Matches 100 Percent

+ References

No definition available.

+ Details

Name:	cmg_DefinedContributionPlanEmployerMatchingContributionPercentOfEmployeesGrossPayAtWhichEmployerMatches100Percent
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay, at Which Employer Matches 50 Percent

+ References

No definition available.

+ Details

Name:	cmg_DefinedContributionPlanEmployerMatchingContributionPercentOfEmployeesGrossPayAtWhichEmployerMatches50Percent
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Contribution Plan, Employer Matching Contribution, Percent of Match On First 3%

+ References

No definition available.

+ Details

Name:	cmg_DefinedContributionPlanEmployerMatchingContributionPercentOfMatchOnFirst3
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Contribution Plan, Employer Matching Contribution, Percent of Match On Next 2 Percent

+ References

No definition available.

+ Details

Name:	cmg_DefinedContributionPlanEmployerMatchingContributionPercentOfMatchOnNext2Percent
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum percent an employee may contribute after one year of service with the Company.

+ References

No definition available.

+ Details

Name:	cmg_EsppPercentOfBaseEarnings
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Eligibility period to contribute to the ESPP.

+ References

No definition available.

+ Details

Name:	cmg_EsppRequisiteServicePeriod
Namespace Prefix:	cmg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Eligibility period to receive matching contributions

+ References

No definition available.

+ Details

Name:	cmg_MatchingContributions401k
Namespace Prefix:	cmg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Purchase price percentage of fair market value of stock on last trading date of monthly exercise period.

+ References

No definition available.

+ Details

Name:	cmg_PurchasePricePercentageOfFairMarketValueOfStockOnLastTradingDateOfMonthlyExercisePeriod
Namespace Prefix:	cmg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement.

+ References

No definition available.

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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_DeferredCompensationArrangementWithIndividualPostretirementBenefitsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

+ References

No definition available.

+ Details

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

- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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

- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis=us-gaap_DomesticPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanNameAxis=cmg_Plan401kMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: