LEASES - Lease costs (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Lessee, Lease, Description [Line Items]
Interest expense on lease liabilities	$ 0.9	$ 1.0	$ 2.8	$ 3.2
Total lease cost	250.3	243.6	723.7	734.2
Depreciation and amortization
Lessee, Lease, Description [Line Items]
Amortization of finance lease assets	0.5	0.6	1.5	2.0
Finance lease obligations
Lessee, Lease, Description [Line Items]
Interest expense on lease liabilities	0.9	0.9	2.8	3.1
60 Theatres \| Rent
Lessee, Lease, Description [Line Items]
Operating lease cost	201.3	202.0	587.5	608.9
Variable lease cost	23.0	21.2	63.3	59.9
60 Theatres \| Operating expense (income)
Lessee, Lease, Description [Line Items]
Operating lease cost	0.6	1.5	1.2	4.1
Equipment \| Operating expense (income)
Lessee, Lease, Description [Line Items]
Operating lease cost	4.8	2.7	11.8	7.4
Variable lease cost	17.9	13.4	51.6	44.8
Office And Other \| General and administrative: other
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 1.3	$ 1.3	$ 4.0	$ 4.0

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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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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