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Fair Value (Fair Value and Unrealized Gains and Losses for the Nuclear Decommissioning Trust Funds) (Details) - DTE Electric - Nuclear decommissioning trust fund - USD ($)
$ in Millions
Mar. 31, 2020
Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]    
Fair Value $ 1,439 $ 1,661
Fixed income securities, fair value 503 538
Private equity and other, fair value 62 43
Cash equivalents, fair value 82 34
Unrealized Gains 270 420
Fixed income securities, unrealized gains 26 24
Unrealized Losses (134) (40)
Fixed income securities, unrealized losses (6) (1)
Equity securities    
Debt Securities, Available-for-sale [Line Items]    
Fair Value 792 1,046
Unrealized Gains 244 396
Unrealized Losses $ (128) $ (39)