Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		$ 1,413			$ 3,286
Leasing income		37			76
Financing income		40			79
Alternative revenue programs		2			4
Total operating revenue		1,492		$ 1,449	3,445		$ 3,278
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		24			48
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,389			3,238
Financing income		4			8
Alternative revenue programs		2			4
Total operating revenue		1,395		1,362	3,250		3,099
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		669			1,707
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		444			967
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		179			346
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		97			218
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,087			2,163
Financing income		2			4
Total operating revenue		1,089		1,077	2,167		2,113
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		302			1,075
Financing income		2			4
Alternative revenue programs		2			4
Total operating revenue		306		285	1,083		986
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	24			48
Leasing income	[1]	37			76
Total operating revenue		61	[1]	55	124	[1]	114
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	24			48
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,087			2,163
Financing income		2			4
Total operating revenue		1,089		1,077	2,167		2,113
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		475			976
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		386			747
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		170			313
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		56			127
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		302			1,075
Financing income		2			4
Alternative revenue programs		2			4
Total operating revenue		306		285	1,083		986
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		194			731
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		58			220
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		9			33
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		41			91
Other reconciling items
Disaggregation of Revenue [Line Items]
Financing income	[2]	36			71
Total operating revenue		36	[2]	$ 32	71	[2]	$ 65
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.