Debt instrument maturity date year.

No definition available.

Name:	mlm_DebtInstrumentMaturityDateYear
Namespace Prefix:	mlm_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ 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 effective interest rate at the end of the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

Long-Term Debt - Long-Term Debt (Parenthetical) (Detail)		12 Months Ended
	Mar. 05, 2020	Dec. 31, 2020	Dec. 31, 2019
4.25% Senior Notes, Due 2024
Debt Instrument [Line Items]
Maturity year		2024
Interest rate on notes		4.25%
Interest rate		4.25%
7% Debentures, Due 2025
Debt Instrument [Line Items]
Maturity year		2025
Interest rate on notes		7.00%
Interest rate		7.12%
3.450% Senior Notes, Due 2027
Debt Instrument [Line Items]
Maturity year		2027
Interest rate on notes		3.45%
Interest rate		3.47%
3.500% Senior Notes, Due 2027
Debt Instrument [Line Items]
Maturity year		2027
Interest rate on notes		3.50%
Interest rate		3.53%
2.500% Senior Notes, Due 2030
Debt Instrument [Line Items]
Maturity year	2030	2030
Interest rate on notes	2.50%	2.50%
Interest rate		2.71%
6.25% Senior Notes, Due 2037
Debt Instrument [Line Items]
Maturity year		2037
Interest rate on notes		6.25%
4.250% Senior Notes, Due 2047
Debt Instrument [Line Items]
Maturity year		2047
Interest rate on notes		4.25%
Interest rate		4.27%
Floating Rate Senior Notes, Due 2020
Debt Instrument [Line Items]
Maturity year		2020
Interest rate			2.55%
Trade Receivable Facility
Debt Instrument [Line Items]
Credit Facility interest rate			2.42%