Leases and Palisades Financing - Schedule of Lease Costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease costs	$ 11
Finance lease costs
Amortization of right-of-use assets	6
Interest on lease liabilities	18
Variable lease costs	95
Total lease costs	130
Consumers Energy Company
Lessee, Lease, Description [Line Items]
Operating lease costs	9
Finance lease costs
Amortization of right-of-use assets	6
Interest on lease liabilities	18
Variable lease costs	95
Total lease costs	$ 128