Other Income and Other Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fee income		$ 6	$ 9
All other	$ 6	2	1
Total other income	6	8	10
Donations	(31)	(23)	(1)
Civic and political expenditures	(27)	(21)	(10)
Loss on reacquired and extinguished debt	(18)	(18)
Unrealized investment loss		(5)
All other		(8)	(6)
Total other expense	(76)	(75)	(17)
Consumers Energy Company [Member]
Gain on CMS Energy common stock	14		9
Fee income		6	9
All other	3	2	1
Total other income	17	8	19
Donations	(31)	(23)	(1)
Civic and political expenditures	(27)	(21)	(10)
Unrealized investment loss		(4)
All other		(7)	(6)
Total other expense	$ (58)	$ (55)	$ (17)