v3.20.4
INVESTMENTS - Rollforwards (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Changes in carrying amount of investment in NCM and equity in losses of NCM      
Balance at the beginning of the period $ 239.1    
Balance at the end of the period $ 80.9 $ 239.1  
Exhibitor Services Agreement      
Common Membership Units rollforward      
Term of amortization of the exhibitor services agreement (ESA) with NCM 30 years    
NCM      
Changes in carrying amount of investment in NCM and equity in losses of NCM      
Balance at the beginning of the period     $ 161.1
Surrender of common units for transferred theatres $ (6.3)   (6.3)
Receipt of excess cash distributions     (15.3)
Impairment loss - held for sale     (14.4)
Sale of common units     (128.3)
Equity in earnings     3.2
NCM | Exhibitor Services Agreement      
Changes in carrying amount of investment in NCM and equity in losses of NCM      
Balance at the beginning of the period (549.7) (564.0) (530.9)
ASC 606 revenue recognition change in amortization method     (52.9)
Surrender of common units for transferred theatres 5.2   5.2
Receipt of common units (4.8) (1.4)  
Amortization of ESA 16.9 15.7 14.6
Balance at the end of the period $ (537.6) (549.7) (564.0)
Common Membership Units rollforward      
Term of amortization of the exhibitor services agreement (ESA) with NCM 30 years    
NCM | Other Comprehensive (Income)      
Changes in carrying amount of investment in NCM and equity in losses of NCM      
Balance at the beginning of the period     (2.5)
Sale of common units     2.4
Equity in earnings     0.1
NCM | Cash Received (Paid)      
Changes in carrying amount of investment in NCM and equity in losses of NCM      
Balance at the beginning of the period   170.7  
Receipt of excess cash distributions     15.3
Expenses on sale of shares     (1.4)
Sale of common units     156.8
Balance at the end of the period     170.7
NCM | Equity in (Earnings)/Loss      
Changes in carrying amount of investment in NCM and equity in losses of NCM      
Balance at the beginning of the period   (17.3)  
Surrender of common units for transferred theatres $ 1.1   1.1
Impairment loss - held for sale     14.4
Expenses on sale of shares     1.4
Sale of common units     (30.9)
Equity in earnings     (3.3)
Balance at the end of the period     (17.3)
NCM | Advertising (Revenue)      
Changes in carrying amount of investment in NCM and equity in losses of NCM      
Balance at the beginning of the period (15.7) (14.6)  
Amortization of ESA (16.9) (15.7) (14.6)
Balance at the end of the period $ (16.9) $ (15.7) $ (14.6)