Retirement Benefits and Trusteed Assets (OPEB - Fair Value Measurements) (Details) - Other postretirement benefit plan - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 1,960	$ 1,819	$ 1,689
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	196	458
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	539	256
Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,225	1,105
Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	21	80
Short-term Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	21	80
Short-term Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Short-term Investments | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Equity Securities, Domestic
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	251	324
Equity Securities, Domestic | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	51	51
Equity Securities, Domestic | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Equity Securities, Domestic | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	200	273
Equity Securities, International
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	201	271
Equity Securities, International | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	23	182
Equity Securities, International | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Equity Securities, International | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	178	89
Fixed Income Securities, Governmental
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	85	74
Fixed Income Securities, Governmental | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	40	74
Fixed Income Securities, Governmental | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	45	0
Fixed Income Securities, Governmental | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Fixed Income Securities, Corporate
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	856	507
Fixed Income Securities, Corporate | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Fixed Income Securities, Corporate | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	477	256
Fixed Income Securities, Corporate | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	379	251
Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	202	253
Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	61	71
Hedge Funds and Similar Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	17	0
Hedge Funds and Similar Investments | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	124	182
Private Equity and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	344	310
Private Equity and Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Private Equity and Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Private Equity and Other | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	344	310
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,320	1,236	$ 1,158
DTE Electric | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	128	310
DTE Electric | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	363	168
DTE Electric | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	829	758
DTE Electric | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	14	55
DTE Electric | Short-term Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	14	55
DTE Electric | Short-term Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Short-term Investments | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Equity Securities, Domestic
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	164	219
DTE Electric | Equity Securities, Domestic | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	33	34
DTE Electric | Equity Securities, Domestic | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Equity Securities, Domestic | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	131	185
DTE Electric | Equity Securities, International
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	133	184
DTE Electric | Equity Securities, International | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	16	124
DTE Electric | Equity Securities, International | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Equity Securities, International | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	117	60
DTE Electric | Fixed Income Securities, Governmental
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	55	48
DTE Electric | Fixed Income Securities, Governmental | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	24	48
DTE Electric | Fixed Income Securities, Governmental | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	31	0
DTE Electric | Fixed Income Securities, Governmental | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Fixed Income Securities, Corporate
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	584	344
DTE Electric | Fixed Income Securities, Corporate | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Fixed Income Securities, Corporate | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	321	168
DTE Electric | Fixed Income Securities, Corporate | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	263	176
DTE Electric | Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	135	172
DTE Electric | Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	41	49
DTE Electric | Hedge Funds and Similar Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	11	0
DTE Electric | Hedge Funds and Similar Investments | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	83	123
DTE Electric | Private Equity and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	235	214
DTE Electric | Private Equity and Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Private Equity and Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Private Equity and Other | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 235	$ 214