v3.24.0.1
SHARE-BASED COMPENSATION (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
2020 FORTIS RESTRICTED STOCK UNIT PLAN      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation, valuation, share equivalent, number (in shares) 1    
Allocated share of probable payout $ 2 $ 2  
Allocated share-based compensation expense $ 1 $ 0 $ 0
2020 FORTIS RESTRICTED STOCK UNIT PLAN | RSUs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options awarded during the period (in shares) 26,980 17,996 20,794
2015 Share Unit Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation, valuation, share equivalent, number (in shares) 1    
Allocated share of probable payout $ 6 $ 4  
Allocated share-based compensation expense $ 3 $ 2 $ 4
2015 Share Unit Plan | RSUs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options awarded during the period (in shares) 2,146 2,409 2,401
2015 Share Unit Plan | PSUs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options awarded during the period (in shares) 58,237 40,793 44,931