XML 75 R58.htm IDEA: XBRL DOCUMENT v3.21.1
Fair Value (Fair Value and Unrealized Gains and Losses for the Nuclear Decommissioning Trust Funds) (Details) - DTE Electric - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]    
Fair Value $ 1,924 $ 1,855
Unrealized Gains 534 501
Unrealized Losses (12) (7)
Cash equivalents    
Debt Securities, Available-for-sale [Line Items]    
Fair Value 20 27
Private equity and other    
Debt Securities, Available-for-sale [Line Items]    
Fair Value 122 104
Unrealized Gains 12 0
Unrealized Losses 0 0
Equity securities    
Debt Securities, Available-for-sale [Line Items]    
Fair Value 1,204 1,169
Unrealized Gains 504 481
Unrealized Losses (6) (6)
Fixed income securities    
Debt Securities, Available-for-sale [Line Items]    
Fair Value 578 555
Unrealized Gains 18 20
Unrealized Losses $ (6) $ (1)