Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		$ 1,873
Leasing income		39
Financing income		39
Total operating revenue		1,953	$ 1,829
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		24
Electric Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,076
Financing income		2
Total operating revenue		1,078
Gas Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		773
Financing income		2
Total operating revenue		777
Enterprises [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	24
Leasing income	[1]	39
Total operating revenue	[1]	63
Enterprises [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	24
Other reconciling items [Member]
Disaggregation of Revenue [Line Items]
Financing income	[2]	35
Total operating revenue	[2]	35
Consumers Energy Company [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,849
Financing income		4
Alternative revenue programs		2
Total operating revenue		1,855	$ 1,737
Consumers Energy Company [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,038
Consumers Energy Company [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		523
Consumers Energy Company [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		167
Consumers Energy Company [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		121
Consumers Energy Company [Member] | Electric Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,076
Financing income		2
Total operating revenue		1,078
Consumers Energy Company [Member] | Electric Utility [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		501
Consumers Energy Company [Member] | Electric Utility [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		361
Consumers Energy Company [Member] | Electric Utility [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		143
Consumers Energy Company [Member] | Electric Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		71
Consumers Energy Company [Member] | Gas Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		773
Financing income		2
Alternative revenue programs		2
Total operating revenue		777
Consumers Energy Company [Member] | Gas Utility [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		537
Consumers Energy Company [Member] | Gas Utility [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		162
Consumers Energy Company [Member] | Gas Utility [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		24
Consumers Energy Company [Member] | Gas Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		$ 50

[1] Amounts represent the enterprises segment's operating revenue from independent power production and CMS ERM's sales of energy commodities in support of the independent power production portfolio.

[2] Amount represents EnerBank's operating revenue from unsecured consumer installment loans for financing home improvements.