Retirement Benefits and Trusteed Assets (OPEB - Postretirement Cost Inclusions) (Details) - Other Postretirement Benefit Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 34	$ 34	$ 47
Interest cost	81	89	88
Expected return on plan assets	(131)	(122)	(110)
Amortization of net actuarial loss	43	20	64
Prior service cost	(126)	(144)	(131)
Net cost (credit)	(99)	(123)	(42)
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Service cost	25	26	35
Interest cost	62	68	67
Expected return on plan assets	(90)	(85)	(74)
Amortization of net actuarial loss	31	14	47
Prior service cost	(95)	(109)	(100)
Net cost (credit)	$ (67)	$ (86)	$ (25)