XML 133 R110.htm IDEA: XBRL DOCUMENT v3.20.4
Fair Value (Fair Value and Unrealized Gains and Losses for the Nuclear Decommissioning Trust Funds) (Details) - DTE Electric - Nuclear decommissioning trusts - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]    
Fair Value $ 1,855 $ 1,661
Fixed income securities, fair value 555 538
Private equity and other, fair value 104 43
Cash equivalents, fair value 27 34
Unrealized gains 501 420
Fixed income securities, unrealized gains 20 24
Unrealized losses (7) (40)
Fixed income securities, unrealized losses (1) (1)
Equity securities    
Debt Securities, Available-for-sale [Line Items]    
Fair Value 1,169 1,046
Unrealized gains 481 396
Unrealized losses $ (6) $ (39)