Represents information about customer.

No definition available.

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Namespace Prefix:	mlr_
Data Type:	xbrli:integerItemType
Balance Type:	na
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
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-Name Accounting Standards Codification
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+ Details

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482861/275-10-50-20

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before allowance for credit loss, of right to consideration in exchange for good or service transferred to customer, when right is conditioned on something other than passage of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 606
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

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

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479837/606-10-45-2

+ Details

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

- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
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-Section 50
-Paragraph 8
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+ Details

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

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MajorCustomersAxis=mlr_CustomerOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

REVENUE - Narrative (Details) $ in Thousands	3 Months Ended	9 Months Ended
REVENUE - Narrative (Details) $ in Thousands	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($) customer	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Concentration Risk [Line Items]
Contract liability balances related to performance obligations	$ 274	$ 242	$ 274			$ 257
Recognized revenue related to contract liability balances		$ 0	0
Contract assets	$ 0		$ 0	$ 0	$ 0
Number of customer \| customer			1
Net sales \| Customer Concentration Risk \| Customer one
Concentration Risk [Line Items]
Concentration Risk, Percentage	12.00%		11.00%