v3.21.1
STOCKHOLDERS' EQUITY - Equity statements (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Feb. 15, 2019
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   $ (2,858.2) $ 1,214.2 $ 1,214.2
Net loss   (566.9) (2,176.3)  
Net loss   (567.2) (2,176.3)  
Other comprehensive loss   (51.2) (93.5)  
Baltics noncontrolling capital contributions   (3.8)    
Class A common stock, accrued dividend equivalent adjustment   (0.1)    
Class A common stock issuance   581.6    
Convertible Notes due 2026 stock conversion   606.5    
Dividends declared $ (3.2)      
Taxes paid for restricted unit withholdings     (1.0)  
Stock-based compensation expense   5.4 2.7  
Balance at the end of the period   (2,287.0) (1,074.0) (2,858.2)
Cumulative Effect, Period of Adoption, Adjustment [Member]        
Increase (Decrease) in Stockholders' Equity        
Balance at the end of the period     (16.9)  
Total AMC Stockholders' Equity (Deficit)        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   (2,885.1)    
Net loss   (566.9)    
Other comprehensive loss   (51.0)    
Baltics noncontrolling capital contribution   0.2    
Class A common stock, accrued dividend equivalent adjustment   (0.1)    
Class A common stock issuance   581.6    
Convertible Notes due 2026 stock conversion   606.5    
Stock-based compensation expense   5.4    
Balance at the end of the period   (2,309.4)   (2,885.1)
Additional Paid-in Capital        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   2,465.6 2,001.9 2,001.9
Baltics noncontrolling capital contribution   0.2    
Class A common stock issuance   579.8    
Convertible Notes due 2026 stock conversion   606.1    
Taxes paid for restricted unit withholdings     (1.0)  
Stock-based compensation expense   5.4 2.7  
Balance at the end of the period   3,657.1 2,003.6 2,465.6
Treasury Stock        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   $ (56.4) $ (56.4) $ (56.4)
Balance (in shares)   3,732,625 3,732,625 3,732,625
Balance at the end of the period   $ (56.4) $ (56.4) $ (56.4)
Balance (in shares)   3,732,625 3,732,625 3,732,625
Accumulated Other Comprehensive Income (Loss)        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   $ 38.7 $ (26.1) $ (26.1)
Other comprehensive loss   (51.0) (93.5)  
Balance at the end of the period   (12.3) (119.6) 38.7
Accumulated Earnings (Deficit)        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   (5,335.3) (706.2) (706.2)
Net loss   (566.9) (2,176.3)  
Class A common stock, accrued dividend equivalent adjustment   (0.1)    
Balance at the end of the period   (5,902.3) (2,902.6) (5,335.3)
Accumulated Earnings (Deficit) | Cumulative Effect, Period of Adoption, Adjustment [Member]        
Increase (Decrease) in Stockholders' Equity        
Balance at the end of the period     (16.9)  
Noncontrolling Interests        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   26.9    
Net loss   (0.3)    
Other comprehensive loss   (0.2)    
Baltics noncontrolling capital contribution   (4.0)    
Balance at the end of the period   $ 22.4   $ 26.9
Class A common stock        
Increase (Decrease) in Stockholders' Equity        
Balance (in shares)   172,563,249    
Balance (in shares)   450,280,240   172,563,249
Class A common stock | Dividend declared        
Increase (Decrease) in Stockholders' Equity        
Dividends declared     (1.6)  
Class A common stock | Common Stock        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   $ 1.8 $ 0.5 $ 0.5
Balance (in shares)   172,563,249 52,080,077 52,080,077
Class A common stock issuance   $ 1.8    
Class A common stock issuance (In shares)   187,066,293    
Wanda conversion of Class B shares to Class A shares   $ 0.5    
Wanda conversion of Class B shares to Class A shares (in shares)   46,103,784    
Convertible Notes due 2026 stock conversion   $ 0.4    
Convertible Notes due 2026 stock conversion (in shares)   44,422,860    
Stock-based compensation (in shares)   124,054 469,516  
Balance at the end of the period   $ 4.5 $ 0.5 $ 1.8
Balance (in shares)   450,280,240 52,549,593 172,563,249
Class A common stock | Accumulated Earnings (Deficit) | Dividend declared        
Increase (Decrease) in Stockholders' Equity        
Dividends declared     $ (1.6)  
Class B common stock        
Increase (Decrease) in Stockholders' Equity        
Balance (in shares)   51,769,784    
Balance (in shares)   0   51,769,784
Class B common stock | Dividend declared        
Increase (Decrease) in Stockholders' Equity        
Dividends declared     (1.6)  
Class B common stock | Common Stock        
Increase (Decrease) in Stockholders' Equity        
Balance at the beginning of the period   $ 0.5 $ 0.5 $ 0.5
Balance (in shares)   51,769,784 51,769,784 51,769,784
Wanda conversion of Class B shares to Class A shares   $ (0.5)    
Wanda conversion of Class B shares to Class A shares (in shares)   (46,103,784)    
Wanda forfeit and cancellation of Class B shares (in shares)   (5,666,000)    
Balance at the end of the period     $ 0.5 $ 0.5
Balance (in shares)     51,769,784 51,769,784
Class B common stock | Accumulated Earnings (Deficit) | Dividend declared        
Increase (Decrease) in Stockholders' Equity        
Dividends declared     $ (1.6)