LEASES - Lease costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Leases:
Interest expense on lease liabilities	$ 1.7	$ 1.4	$ 3.2	$ 2.6
Total lease cost	266.6	261.3	522.5	502.9
Location, Statement of Income, Balance [Axis]: us-gaap:DepreciationDepletionAndAmortization
Leases:
Amortization of finance lease assets	0.9	0.7	1.6	1.4
Location, Statement of Income, Balance [Axis]: us-gaap:FinanceLeaseInterestExpense
Leases:
Interest expense on lease liabilities	0.9	0.8	1.7	1.6
Theatre properties \| Location, Statement of Income, Balance [Axis]: us-gaap:FinanceLeaseInterestExpense
Leases:
Variable operating and finance lease cost	0.9	0.6	1.5	1.0
Theatre properties \| Location, Statement of Income, Balance [Axis]: us-gaap:OperatingLeaseExpense
Leases:
Operating lease cost	193.5	193.4	385.6	383.6
Variable operating and finance lease cost	30.3	29.2	62.3	57.1
Theatre properties \| Location, Statement of Income, Balance [Axis]: us-gaap:OtherCostAndExpenseOperating
Leases:
Operating lease cost	1.5	2.2	2.8	3.4
Equipment \| Location, Statement of Income, Balance [Axis]: us-gaap:OtherCostAndExpenseOperating
Leases:
Operating lease cost	12.8	10.4	25.4	20.1
Variable operating and finance lease cost	24.6	22.6	39.2	32.0
Office and other \| Location, Statement of Income, Balance [Axis]: us-gaap:OtherGeneralAndAdministrativeExpense
Leases:
Operating lease cost	$ 1.2	$ 1.4	$ 2.4	$ 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
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

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- Definition

Amount of lease cost recognized by lessee for lease contract.

+ References

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- Definition

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
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- Definition

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.

+ References

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- Definition

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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