Loss Contingency, Domicile of Litigation, Number of States or Provinces

No definition available.

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- Definition

Proceeds from Insurance Recoveries

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

The amount recovered from insurance. These recoveries reduce costs and losses that are reported as a separate line item under operating expenses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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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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- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14435-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14557-108349

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12021-110248

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of loss pertaining to the specified contingency that was charged against earnings in the period, including the effects of revisions in previously reported estimates.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

+ Details

Name:	us-gaap_LossContingencyNewClaimsFiledNumber
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

Name:	us-gaap_LossContingencyPendingClaimsNumber
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Balance Type:	na
Period Type:	instant

- Details

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- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=mar_DataSecurityIncidentUKInformationCommissionersOfficeMember
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- Details

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- Details

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Commitments and Contingencies - Expenses and Insurance Recoveries (Details) £ in Millions, $ in Millions	1 Months Ended	3 Months Ended
	Mar. 15, 2019 lawsuit	Mar. 31, 2020 USD ($) lawsuit province	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jul. 31, 2019 GBP (£)
Loss Contingencies [Line Items]
Insurance recoveries received		$ 24	$ 40
Data Security Incident
Loss Contingencies [Line Items]
Expense related to data security incident		15	44
Insurance recoveries related to data security incident		$ 17	$ 46
Data Security Incident, UK Information Commissioner's Office
Loss Contingencies [Line Items]
Estimated fine \| £					£ 99
Accrual for loss contingency				$ 65
Putative Class Action Lawsuits Related to Data Security Incident
Loss Contingencies [Line Items]
Number of lawsuits filed \| lawsuit		100
Shareholder Derivative Complaints Related to Data Security Incident
Loss Contingencies [Line Items]
Number of new lawsuits filed \| lawsuit	2
Canadian Putative Class Action Lawsuits Related to Data Security Incident
Loss Contingencies [Line Items]
Number of lawsuits filed \| lawsuit		5
Number of provinces where cases are pending \| province		5