Retirement Benefits and Trusteed Assets (OPEB - Fair Value Measurements) (Details) - Other postretirement benefit plan - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 1,848	$ 1,758	$ 1,617
Assets valued at NAV	660	587
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	861	870
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	327	301
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	15	40
Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	13	39
Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	2	1
U.S. Large Capitalization (Cap) Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	284	284
U.S. Large Capitalization (Cap) Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	284	284
U.S. Large Capitalization (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	131	156
U.S. Small Cap and Mid Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	131	156
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	366	324
Assets valued at NAV	77	61
Non-U.S. Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	288	262
Non-U.S. Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1	1
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	483	439
Assets valued at NAV	130	125
Fixed Income Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	29	15
Fixed Income Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	324	299
Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	335	338
Assets valued at NAV	219	224
Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	116	114
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	234	177
Assets valued at NAV	234	177
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	(40)	(31)
Securities lending | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(39)	(28)
Securities lending | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(1)	(3)
Securities lending collateral
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	40	31
Securities lending collateral | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	39	28
Securities lending collateral | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1	3
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,272	1,218	$ 1,131
Assets valued at NAV	457	409
DTE Electric | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	595	604
DTE Electric | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	220	205
DTE Electric | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	10	29
DTE Electric | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	9	28
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 Capitalization (Cap) Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	195	195
DTE Electric | U.S. Large Capitalization (Cap) Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	195	195
DTE Electric | U.S. Large Capitalization (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	91	109
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	91	109
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	253	224
Assets valued at NAV	52	41
DTE Electric | Non-U.S. Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	200	182
DTE Electric | Non-U.S. Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1	1
DTE Electric | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	330	303
Assets valued at NAV	92	90
DTE Electric | Fixed Income Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	20	10
DTE Electric | Fixed Income Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	218	203
DTE Electric | Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	230	234
Assets valued at NAV	150	154
DTE Electric | Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	80	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	163	124
Assets valued at NAV	163	124
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	(28)	(21)
DTE Electric | Securities lending | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(27)	(20)
DTE Electric | Securities lending | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	(1)	(1)
DTE Electric | Securities lending collateral
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	28	21
DTE Electric | Securities lending collateral | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	27	20
DTE Electric | Securities lending collateral | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 1	$ 1