Leases And Palisades Financing (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) MW	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Consumers Energy Company [Member]
Leases [Line Items]
Finance Lease Term	15 years
Consumers Energy Company [Member] | Scenario, Plan [Member]
Leases [Line Items]
Lease termination cost		$ 172
Authorized recovery of lease termination cost	$ 137
Coal-Carrying Railcars [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Operating leases without extension provisions, remaining term	6 years
Operating leases with extension provisions, remaining term	9 years
Gas Transportation Pipeline into Karn [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Capital Lease Term	15 years
Capital Lease Remaining Term	4 years
Gas Transportation Pipeline into Zeeland [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Capital Lease Term	5 years
Minimum [Member] | Coal-Carrying Railcars [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Operating leases, term	2 years
Minimum [Member] | Gas Transportation Pipeline into Zeeland [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Capital lease renewal term	5 years
Minimum [Member] | Long-term PPAs [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Lease term	1 year
Maximum [Member] | Coal-Carrying Railcars [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Operating leases, term	15 years
Maximum [Member] | Vehicle Fleet Operations [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Capital Lease Term	120 months
Maximum [Member] | Gas Transportation Pipeline into Zeeland [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Capital lease renewal term	10 years
Maximum [Member] | Long-term PPAs [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Lease term	15 years
Capital Leases [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments	$ 58
Financing Leases [Member]
Leases [Line Items]
Finance Leases Lessee Balance Sheet Assets Amortization And Interest Charges	17	$ 17	$ 18
Financing Leases [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments	$ 55
Palisades PPA [Member]
Leases [Line Items]
Unrecorded Unconditional Purchase Obligations, Maximum Quantity | MW	798
Palisades PPA [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Unrecorded Unconditional Purchase Obligations, Maximum Quantity | MW	798