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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
Jun. 30, 2020
Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]    
Fair Value $ 1,603 $ 1,661
Fixed income securities, fair value 509 538
Private equity and other, fair value 62 43
Cash equivalents, fair value 59 34
Unrealized Gains 297 420
Fixed income securities, unrealized gains 35 24
Unrealized Losses (27) (40)
Fixed income securities, unrealized losses (2) (1)
Equity securities    
Debt Securities, Available-for-sale [Line Items]    
Fair Value 973 1,046
Unrealized Gains 262 396
Unrealized Losses $ (25) $ (39)