LEASES - Lease costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Lessee, Lease, Description [Line Items]
Interest expense on lease liabilities	$ 1.0	$ 1.0	$ 1.9	$ 2.2
Total lease cost	248.3	247.5	473.4	490.6
Depreciation and amortization
Lessee, Lease, Description [Line Items]
Amortization of finance lease assets	0.5	0.7	1.0	1.4
Finance lease obligations
Lessee, Lease, Description [Line Items]
Interest expense on lease liabilities	1.0	1.0	1.9	2.2
58 Theatres \| Rent
Lessee, Lease, Description [Line Items]
Operating lease cost	202.0	204.4	386.2	406.9
Variable lease cost	18.8	18.0	40.3	38.7
58 Theatres \| Operating expense (income)
Lessee, Lease, Description [Line Items]
Operating lease cost	0.3	1.4	0.6	2.6
Equipment \| Operating expense (income)
Lessee, Lease, Description [Line Items]
Operating lease cost	3.9	1.9	7.0	4.7
Variable lease cost	20.4	18.8	33.7	31.4
Office And Other \| General and administrative: other
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 1.4	$ 1.3	$ 2.7	$ 2.7

Amount of interest expense on finance lease liability.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 53
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479589/842-20-55-53

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479041/842-20-45-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147478964/842-20-50-4

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- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

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- Definition

Amount of lease cost recognized by lessee for lease contract.

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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.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147478964/842-20-50-3

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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

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Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

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