Retirement Benefits and Trusteed Assets (OPEB - Reconciliation of Obligations, Assets and Funded Status of Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in Regulatory assets
Regulatory assets	$ 3,778	$ 3,913
Other postretirement benefit plan
Change in accumulated postretirement benefit obligation
Projected/Accumulated postretirement benefit obligation, beginning of year	1,795	1,846
Service cost	27	27	$ 34
Interest cost	73	80	81
Actuarial (gain) loss	101	(75)
Benefits paid	(86)	(83)
Projected/Accumulated postretirement benefit obligation, end of year	1,910	1,795	1,846
Change in plan assets
Plan assets at fair value, beginning of year	1,758	1,617
Actual return on plan assets	252	122
Company contributions	0	20
Benefits paid	(162)	(1)
Plan assets at fair value, end of year	1,848	1,758	1,617
Funded status	(62)	(37)
Amount recorded as:
Noncurrent assets	0	0
Current liabilities	(1)	(1)
Noncurrent liabilities	(61)	(36)
Defined benefit plans liabilities	(62)	(37)
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax
Net actuarial loss	(1)	12
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax	(1)	12
Amounts recognized in Regulatory assets
Net actuarial loss	279	300
Prior service credit	(1)	(14)
Regulatory assets	278	286
DTE Electric
Amounts recognized in Regulatory assets
Regulatory assets	3,055	3,149
DTE Electric | Other postretirement benefit plan
Change in accumulated postretirement benefit obligation
Projected/Accumulated postretirement benefit obligation, beginning of year	1,373	1,414
Service cost	20	20	25
Interest cost	56	61	62
Actuarial (gain) loss	84	(62)
Benefits paid	(63)	(60)
Projected/Accumulated postretirement benefit obligation, end of year	1,470	1,373	1,414
Change in plan assets
Plan assets at fair value, beginning of year	1,218	1,131
Actual return on plan assets	172	87
Company contributions	0	0
Benefits paid	(118)	0
Plan assets at fair value, end of year	1,272	1,218	$ 1,131
Funded status	(198)	(155)
Amount recorded as:
Noncurrent assets	113	114
Current liabilities	0	0
Noncurrent liabilities	(311)	(269)
Defined benefit plans liabilities	(198)	(155)
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax
Net actuarial loss	0	0
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax	0	0
Amounts recognized in Regulatory assets
Net actuarial loss	211	217
Prior service credit	0	(10)
Regulatory assets	$ 211	$ 207