Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		$ 1,519			$ 4,805
Leasing income		36			112
Financing income		43			122
Alternative revenue programs		1			5
Total operating revenue		1,599		$ 1,527	5,044		$ 4,805
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		21			69
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,498			4,736
Financing income		3			11
Alternative revenue programs		1			5
Total operating revenue		1,502		1,437	4,752		4,536
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		743			2,450
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		464			1,431
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		190			536
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		101			319
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,310			3,473
Financing income		3			7
Total operating revenue		1,313		1,247	3,480		3,360
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		188			1,263
Financing income		0			4
Alternative revenue programs		1			5
Total operating revenue		189		190	1,272		1,176
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	21			69
Leasing income	[1]	36			112
Total operating revenue		57	[1]	58	181	[1]	172
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	21			69
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,310			3,473
Financing income		3			7
Total operating revenue		1,313		1,247	3,480		3,360
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		625			1,601
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		434			1,181
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		186			499
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		65			192
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		188			1,263
Financing income		0			4
Alternative revenue programs		1			5
Total operating revenue		189		190	1,272		1,176
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		118			849
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		30			250
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		4			37
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		36			127
Other reconciling items
Disaggregation of Revenue [Line Items]
Financing income	[2]	40			111
Total operating revenue		40	[2]	$ 32	111	[2]	$ 97
Other reconciling items | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Total operating revenue		$ 0			$ 0

[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.