XML 118 R92.htm IDEA: XBRL DOCUMENT v3.3.1.900
Fair Value (Fair Value and Unrealized Gains and Losses for the Nuclear Decommissioning Trust Funds) (Details) - DTE Electric - USD ($)
$ in Millions
Dec. 31, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Nuclear decommissioning trusts $ 1,236 $ 1,241
Gross Unrealized Gain 211 225
Gross Unrealized Loss (72) (41)
Nuclear Decommissioning Trust Fund    
Schedule of Available-for-sale Securities [Line Items]    
Equity Securities 731 756
Debt Securities 499 474
Cash equivalents 6 11
Equity Securities, Gross Unrealized Gain 195 204
Equity Securities, Gross Unrealized Loss (68) (39)
Debt Securities, Gross Unrealized Gain 16 21
Debt Securities, Gross Unrealized Loss $ (4) $ (2)