Other Income and Other Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Income and Expenses [Line Items]
Donations	$ (35)	$ (3)	$ (13)
Civic and political expenditures	(5)	(6)	(6)
Loss on reacquired and extinguished debt	(16)	0	(16)
All other	(6)	(4)	(13)
Total other expense	(62)	(13)	(48)
Consumers Energy Company
Other Income and Expenses [Line Items]
Donations	(33)	(3)	(13)
Civic and political expenditures	(5)	(6)	(6)
All other	(5)	(4)	(11)
Total other expense	$ (43)	$ (13)	$ (30)