Retirement Benefits and Trusteed Assets (OPEB - Fair Value Measurements) (Details) - Other postretirement benefit plan - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 1,689	$ 1,848	$ 1,758
Assets valued at NAV	681	660
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	656	861
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	352	327
Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	16	15
Short-term Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	14	13
Short-term Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	2	2
U.S. Large Cap Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	225	284
U.S. Large Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	225	284
U.S. Large Cap Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
U.S. Small Cap and Mid Cap Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	75	131
U.S. Small Cap and Mid Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	75	131
U.S. Small Cap and Mid Cap Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Non-U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	301	366
Assets valued at NAV	67	77
Non-U.S. Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	234	288
Non-U.S. Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	1
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	491	483
Assets valued at NAV	130	130
Fixed Income Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	11	29
Fixed Income Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	350	324
Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	300	335
Assets valued at NAV	203	219
Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	97	116
Hedge Funds and Similar Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Private Equity and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	281	234
Assets valued at NAV	281	234
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
Securities Lending
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(22)	(40)
Securities Lending | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(21)	(39)
Securities Lending | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(1)	(1)
Securities Lending Collateral
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	22	40
Securities Lending Collateral | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	21	39
Securities Lending Collateral | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1	1
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,158	1,272	$ 1,218
Assets valued at NAV	471	457
DTE Electric | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	454	595
DTE Electric | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	233	220
DTE Electric | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	11	10
DTE Electric | Short-term Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	10	9
DTE Electric | Short-term Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1	1
DTE Electric | U.S. Large Cap Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	154	195
DTE Electric | U.S. Large Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	154	195
DTE Electric | U.S. Large Cap Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	52	91
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	52	91
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Non-U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	208	253
Assets valued at NAV	45	52
DTE Electric | Non-U.S. Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	163	200
DTE Electric | Non-U.S. Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	1
DTE Electric | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	331	330
Assets valued at NAV	92	92
DTE Electric | Fixed Income Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	7	20
DTE Electric | Fixed Income Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	232	218
DTE Electric | Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	207	230
Assets valued at NAV	139	150
DTE Electric | Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	68	80
DTE Electric | Hedge Funds and Similar Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
DTE Electric | Private Equity and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	195	163
Assets valued at NAV	195	163
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 | Securities Lending
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(15)	(28)
DTE Electric | Securities Lending | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(15)	(27)
DTE Electric | Securities Lending | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	(1)
DTE Electric | Securities Lending Collateral
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	15	28
DTE Electric | Securities Lending Collateral | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	15	27
DTE Electric | Securities Lending Collateral | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 0	$ 1