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Revenue - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Revenue from External Customer [Line Items]    
Allowance for doubtful accounts receivable write-offs $ 29 $ 25
DTE Electric    
Revenue from External Customer [Line Items]    
Allowance for doubtful accounts receivable write-offs $ 16 $ 14