STOCKHOLDERS' EQUITY - Equity statements (Details) - USD ($) $ in Millions			3 Months Ended						9 Months Ended
	Aug. 25, 2023	Feb. 07, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Increase (Decrease) in Stockholders' Equity
Balance at the beginning of the period			$ (2,582.6)	$ (2,590.3)	$ (2,624.5)	$ (2,326.8)	$ (2,178.3)	$ (1,789.5)	$ (2,624.5)	$ (1,789.5)
Net earnings (loss)			12.3	8.6	(235.5)	(226.9)	(121.6)	(337.4)	$ (214.6)	(685.9)
Other comprehensive loss			9.2	(40.0)	(7.3)	(26.0)	(46.3)	(5.8)
AMC Preferred Equity Unit conversion (in shares)	99,540,642
Settlement payment			99.3
Share issuance			316.5	32.7	70.5	4.3
Share issuance (in shares)									40,000,000.0
Taxes paid for restricted unit withholdings				(1.1)	(13.1)			(52.2)
Stock-based compensation			7.3	7.5	25.9		19.4	6.6
Stock-based compensation						(3.6)
Balance at the end of the period			(2,138.0)	(2,582.6)	(2,590.3)	(2,579.0)	(2,326.8)	$ (2,178.3)	$ (2,138.0)	(2,579.0)
Net proceeds from AMC Preferred Equity Units issuance									492.4	7.8
Carrying value of corporate borrowings			4,664.4						4,664.4		$ 4,949.0
Second Lien Notes due 2026
Increase (Decrease) in Stockholders' Equity
Share issuance		$ 193.7
Carrying value of corporate borrowings					118.6
Forward purchase agreement
Increase (Decrease) in Stockholders' Equity
Share issuance					$ 193.7
Board of Directors
Increase (Decrease) in Stockholders' Equity
Shares awarded					8,555			4,165
RSUs and PSUs vested					226,791			279,985
Preferred Stock
Increase (Decrease) in Stockholders' Equity
Balance at the beginning of the period			0.1	0.1	$ 0.1	0.1	0.1	$ 0.1	0.1	0.1
AMC Preferred Equity Unit conversion			(0.1)
Balance at the end of the period				0.1	0.1	0.1	0.1	0.1		0.1
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity
Balance at the beginning of the period			5,365.9	5,326.8	5,049.8	4,835.7	4,816.3	4,862.0	5,049.8	4,862.0
AMC Preferred Equity Unit conversion			(0.9)
Settlement payment			99.2
Share issuance			316.1	32.7	70.5	4.3
Taxes paid for restricted unit withholdings				(1.1)	(13.1)			(52.2)
Stock-based compensation			7.3	7.5	25.9		19.4	6.5
Stock-based compensation						(3.6)
Balance at the end of the period			5,787.6	5,365.9	5,326.8	4,836.4	4,835.7	4,816.3	5,787.6	4,836.4
Additional Paid-in Capital | Forward purchase agreement
Increase (Decrease) in Stockholders' Equity
Share issuance					193.7
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity
Balance at the beginning of the period			(124.6)	(84.6)	(77.3)	(80.2)	(33.9)	(28.1)	(77.3)	(28.1)
Other comprehensive loss			9.2	(40.0)	(7.3)	(26.0)	(46.3)	(5.8)
Balance at the end of the period			(115.4)	(124.6)	(84.6)	(106.2)	(80.2)	(33.9)	(115.4)	(106.2)
Accumulated Earnings (Deficit)
Increase (Decrease) in Stockholders' Equity
Balance at the beginning of the period			(7,824.5)	(7,833.1)	(7,597.6)	(7,083.0)	(6,961.4)	(6,624.0)	(7,597.6)	(6,624.0)
Net earnings (loss)			12.3	8.6	(235.5)	(226.9)	(121.6)	(337.4)
Balance at the end of the period			(7,812.2)	(7,824.5)	(7,833.1)	(7,309.9)	(7,083.0)	(6,961.4)	(7,812.2)	(7,309.9)
Class A common stock | Common Stock
Increase (Decrease) in Stockholders' Equity
Balance at the beginning of the period			$ 0.5	$ 0.5	$ 0.5	$ 0.6	$ 0.6	$ 0.5	$ 0.5	$ 0.5
Balance (in shares)			51,919,238	51,919,238	51,683,892	51,682,060	51,682,060	51,397,910	51,683,892	51,397,910
AMC Preferred Equity Unit conversion			$ 1.0
AMC Preferred Equity Unit conversion (in shares)			99,540,642
Settlement payment			$ 0.1
Settlement payment (In shares)			6,897,018
Share issuance			$ 0.4
Share issuance (in shares)			40,000,000
Stock-based compensation								$ 0.1
Stock-based compensation (in shares)					235,346			284,150
Balance at the end of the period			$ 2.0	$ 0.5	$ 0.5	$ 0.6	$ 0.6	$ 0.6	$ 2.0	$ 0.6
Balance (in shares)			198,356,898	51,919,238	51,919,238	51,682,060	51,682,060	51,682,060	198,356,898	51,682,060
Series A Convertible Participating Preferred Stock | Preferred Stock
Increase (Decrease) in Stockholders' Equity
Balance (in shares)			9,954,065	9,741,909	7,245,872	5,168,206	5,168,206	5,139,791	7,245,872	5,139,791
AMC Preferred Equity Unit conversion (in shares)			(9,954,065)
Share issuance (in shares)				212,156	492,880	27,000
Stock-based compensation (in shares)					26,944			28,415
Balance (in shares)				9,954,065	9,741,909	5,195,206	5,168,206	5,168,206		5,195,206
Series A Convertible Participating Preferred Stock | Preferred Stock | Forward purchase agreement
Increase (Decrease) in Stockholders' Equity
Share issuance (in shares)					1,976,213
AMC Preferred Stock Depository Shares | Preferred Stock
Increase (Decrease) in Stockholders' Equity
Balance (in shares)			99,540,642	97,419,080	72,458,706	51,682,060	51,682,060	51,397,910	72,458,706	51,397,910
AMC Preferred Equity Unit conversion (in shares)			(99,540,642)
Share issuance (in shares)				2,121,562	4,928,800	270,000
Stock-based compensation (in shares)					269,444			284,150
Balance (in shares)				99,540,642	97,419,080	51,952,060	51,682,060	51,682,060		51,952,060
AMC Preferred Stock Depository Shares | Preferred Stock | Forward purchase agreement
Increase (Decrease) in Stockholders' Equity
Share issuance (in shares)					19,762,130
AMC Preferred Equity Units
Increase (Decrease) in Stockholders' Equity
Net proceeds from AMC Preferred Equity Units issuance		$ 75.1			$ 75.1
AMC Preferred Equity Units | Second Lien Notes due 2026
Increase (Decrease) in Stockholders' Equity
Share issuance (in shares)		19,762,130
AMC Preferred Equity Units | Board of Directors
Increase (Decrease) in Stockholders' Equity
Shares awarded					15,370			4,165
RSUs and PSUs vested					254,074			279,985