Significant Accounting Policies (Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 9,990	$ 9,499	$ 8,795
Net current-period Other comprehensive income (loss)	5	13	12
Ending balance	10,717	9,990	9,499
AOCI including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(120)	(133)
Implementation of ASU 2016-01				$ (5)
Other comprehensive income (loss) before reclassifications	(5)	(1)
Amounts reclassified from Accumulated other comprehensive income	10	14
Net current-period Other comprehensive income (loss)	0	13
Ending balance	(120)	(120)	(133)
Net Unrealized Gain (Loss) on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(3)	(4)
Implementation of ASU 2016-01				(7)
Other comprehensive income (loss) before reclassifications	(2)	0
Amounts reclassified from Accumulated other comprehensive income	1	1
Net current-period Other comprehensive income (loss)	(8)	1
Ending balance	(11)	(3)	(4)
Net Unrealized Gain (Loss) on Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(2)	(3)
Implementation of ASU 2016-01				2
Other comprehensive income (loss) before reclassifications	0	1
Amounts reclassified from Accumulated other comprehensive income	0	0
Net current-period Other comprehensive income (loss)	2	1
Ending balance	0	(2)	(3)
Benefit Obligations
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(110)	(120)
Implementation of ASU 2016-01				0
Other comprehensive income (loss) before reclassifications	(1)	(3)
Amounts reclassified from Accumulated other comprehensive income	9	13
Net current-period Other comprehensive income (loss)	8	10
Ending balance	(102)	(110)	(120)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(5)	(6)
Implementation of ASU 2016-01				$ 0
Other comprehensive income (loss) before reclassifications	(2)	1
Amounts reclassified from Accumulated other comprehensive income	0	0
Net current-period Other comprehensive income (loss)	(2)	1
Ending balance	(7)	(5)	(6)
DTE Electric
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net current-period Other comprehensive income (loss)	$ 0	$ 1	$ 0