Retirement Benefits and Trusteed Assets (OPEB - Fair Value Measurements) (Details) - Other Postretirement Benefit Plan - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	$ 1,617	$ 1,528	$ 1,527
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	803	765
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	490	464
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	324	299	260
Short-term Investments (b)
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	7	6
Short-term Investments (b) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	7	6
Short-term Investments (b) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
Short-term Investments (b) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
U.S. Large Capitalization (Cap) Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	264	266
U.S. Large Capitalization (Cap) Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	264	266
U.S. Large Capitalization (Cap) Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
U.S. Large Capitalization (Cap) Equity Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
U.S. Small Cap and Mid Cap Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	138	149
U.S. Small Cap and Mid Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	138	149
U.S. Small Cap and Mid Cap Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
U.S. Small Cap and Mid Cap Equity Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
Non-U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	317	281
Non-U.S. Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	262	222
Non-U.S. Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	55	59
Non-U.S. Equity Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	413	375
Fixed Income Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	23	15
Fixed Income Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	390	360
Fixed Income Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	325	320
Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	109	107
Hedge Funds and Similar Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	45	45
Hedge Funds and Similar Investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	171	168	159
Private Equity and Other
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	153	131
Private Equity and Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
Private Equity and Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
Private Equity and Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	153	131	101
Securities Lending (i)
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	(128)	(158)
Securities Lending (i) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	(122)	(141)
Securities Lending (i) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	(6)	(17)
Securities Lending (i) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
Securities Lending Collateral (i)
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	128	158
Securities Lending Collateral (i) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	122	141
Securities Lending Collateral (i) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	6	17
Securities Lending Collateral (i) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	1,131	1,038	1,061
DTE Electric | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	562	520
DTE Electric | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	341	313
DTE Electric | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	228	205	182
DTE Electric | Short-term Investments (b)
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	5	4
DTE Electric | Short-term Investments (b) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	5	4
DTE Electric | Short-term Investments (b) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | Short-term Investments (b) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | U.S. Large Capitalization (Cap) Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	183	179
DTE Electric | U.S. Large Capitalization (Cap) Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	183	179
DTE Electric | U.S. Large Capitalization (Cap) Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | U.S. Large Capitalization (Cap) Equity Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	97	102
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	97	102
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | U.S. Small Cap and Mid Cap Equity Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | Non-U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	221	190
DTE Electric | Non-U.S. Equity Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	184	151
DTE Electric | Non-U.S. Equity Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	37	39
DTE Electric | Non-U.S. Equity Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	289	254
DTE Electric | Fixed Income Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	17	11
DTE Electric | Fixed Income Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	272	243
DTE Electric | Fixed Income Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	227	218
DTE Electric | Hedge Funds and Similar Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	76	73
DTE Electric | Hedge Funds and Similar Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	32	31
DTE Electric | Hedge Funds and Similar Investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	119	114	111
DTE Electric | Private Equity and Other
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	109	91
DTE Electric | Private Equity and Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | Private Equity and Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | Private Equity and Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	109	91	$ 71
DTE Electric | Securities Lending (i)
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	(91)	(109)
DTE Electric | Securities Lending (i) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	(87)	(98)
DTE Electric | Securities Lending (i) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	(4)	(11)
DTE Electric | Securities Lending (i) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	0	0
DTE Electric | Securities Lending Collateral (i)
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	91	109
DTE Electric | Securities Lending Collateral (i) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	87	98
DTE Electric | Securities Lending Collateral (i) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	4	11
DTE Electric | Securities Lending Collateral (i) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value plan asset	$ 0	$ 0