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Significant Accounting Policies (Intangible Assets) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]    
Accumulated Amortization $ (98) $ (83)
Indefinite-lived Intangible Assets [Line Items]    
Intangible assets not subject to amortization 4 11
Long-term intangible assets    
Gross Carrying Value 275 282
Accumulated Amortization (98) (83)
Net Carrying Value 177 199
DTE Electric    
Indefinite-lived Intangible Assets [Line Items]    
Intangible assets not subject to amortization 2 11
Contract intangibles    
Finite-Lived Intangible Assets [Line Items]    
Gross Carrying Value 271 271
Accumulated Amortization (98) (83)
Net Carrying Value 173 188
Long-term intangible assets    
Accumulated Amortization $ (98) $ (83)
Contract intangibles | Minimum    
Finite-Lived Intangible Assets [Line Items]    
Useful Lives 6 years  
Contract intangibles | Maximum    
Finite-Lived Intangible Assets [Line Items]    
Useful Lives 26 years