Annual report pursuant to Section 13 and 15(d)

BENEFIT PLANS - Reconciliation of Beginning and Ending Balances for Plan Assets Valued using Significant Unobservable Inputs (Details)

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BENEFIT PLANS - Reconciliation of Beginning and Ending Balances for Plan Assets Valued using Significant Unobservable Inputs (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Private Equity    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Roll Forward]    
Beginning balance $ 9.8 $ 12.9
Return on plan assets:    
Unrealized 3.4 (0.1)
Realized 2.2 (1.0)
Purchases 4.8 0.1
Sales (4.1) (2.1)
Ending balance 16.1 9.8
Hedge Funds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Roll Forward]    
Beginning balance 15.3 36.3
Return on plan assets:    
Unrealized (2.1) 0.0
Realized 2.1 (1.3)
Purchases 0.0 0.0
Sales (15.2) (19.7)
Ending balance 0.1 15.3
Real Assets    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Roll Forward]    
Beginning balance 16.3 18.9
Return on plan assets:    
Unrealized (0.6) (0.1)
Realized 0.2 0.1
Purchases 0.1 0.1
Sales (11.6) (2.7)
Ending balance $ 4.4 $ 16.3