BASIS OF PRESENTATION - Impairment narratives (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($) item
Impairment losses
Impairment of long-lived assets		$ 91.3
Impairment of definite-lived intangible assets		8.0
Impairment of other assets recorded in investment expense (income)		7.2
Impairment of indefinite-lived intangible assets	$ 0.0	8.3
Goodwill impairment		1,744.3
Domestic theatres
Impairment losses
Impairment of definite-lived intangible assets		8.0
Goodwill impairment		1,124.9
International theatres
Impairment losses
Impairment of long-lived assets		$ 9.9
Tangible asset impairment, number of theatres \| item		23
Tangible asset impairment, number of screens \| item		213
Goodwill impairment		$ 619.4
Oden trade name
Impairment losses
Impairment of indefinite-lived intangible assets		5.9
Nordic trade names
Impairment losses
Impairment of indefinite-lived intangible assets		2.4
U.S.
Impairment losses
Impairment of long-lived assets		$ 81.4
Tangible asset impairment, number of theatres \| item		57
Tangible asset impairment, number of screens \| item		658
International markets
Impairment losses
Impairment of long-lived assets		$ 9.9
Tangible asset impairment, number of theatres \| item		23
Tangible asset impairment, number of screens \| item		213

The number of screens in theatres for which tangible asset impairment charges were recorded.

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The number of theatres for which tangible asset impairment charges were recorded.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

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Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

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The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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