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Earnings Per Share and Dividends (Reconciliation of Basic and Diluted Earnings Per Share Calculation) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Basic and Diluted Earnings per Common Share    
Net Income Attributable to DT Midstream $ 81 $ 81
Average number of common shares outstanding — basic (in shares) 96.8 96.7
Incremental shares attributable to:    
Average dilutive restricted stock units and performance share awards (in shares) 0.6 0.3
Average number of common shares outstanding — diluted (in shares) 97.4 97.0
Basic earnings per common share (in dollars per share) $ 0.84 $ 0.84
Diluted earnings per common share (in dollars per share) $ 0.84 $ 0.84