SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 29, 2020	Dec. 29, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Number of years of pre-tax losses	3 years
Valuation allowance charge	$ 8.5
Valuation allowance against majority of deferred tax assets		$ 176.1
Valuation allowance	$ 184.6

Number of years of cumulative pre-tax losses incurred by the entity.

No definition available.

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- Definition

Amount of valuation allowance charge reducing the majority of deferred tax assets.

+ References

No definition available.

+ Details

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- Definition

The amount of valuation allowance charge recorded in the consolidated statements of operations.

+ References

No definition available.

+ Details

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Namespace Prefix:	mni_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- References

No definition available.

+ Details

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

+ Details

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