Revenue (Components of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									$ 6,502
Leasing income									160
Financing income									172
Consumers alternative revenue programs									39
Total operating revenue	$ 1,829	$ 1,599	$ 1,492	$ 1,953	$ 1,778	$ 1,527	$ 1,449	$ 1,829	6,873	$ 6,583	$ 6,399
Other reconciling items
Disaggregation of Revenue [Line Items]
Financing income									157
Total operating revenue									157	132	120
Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									4,528
Financing income									10
Consumers alternative revenue programs									23
Total operating revenue									4,561	4,448	4,379
Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									1,882
Financing income									5
Consumers alternative revenue programs									16
Total operating revenue									1,903	1,774	1,685
Enterprises | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									92
Leasing income									160
Total operating revenue									252	229	215
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									6,410
Leasing income									0
Financing income									15
Consumers alternative revenue programs									39
Total operating revenue	$ 1,712	$ 1,502	$ 1,395	$ 1,855	$ 1,686	$ 1,437	$ 1,362	$ 1,737	6,464	6,222	6,064
Consumers Energy Company | Other reconciling items
Disaggregation of Revenue [Line Items]
Total operating revenue									0
Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									4,528
Financing income									10
Consumers alternative revenue programs									23
Total operating revenue									4,561	4,448	4,379
Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									1,882
Financing income									5
Consumers alternative revenue programs									16
Total operating revenue									1,903	$ 1,774	$ 1,685
Consumers Energy Company | Enterprises | Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenue									0
Residential | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									3,333
Residential | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									2,049
Residential | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									1,284
Commercial | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									1,912
Commercial | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									1,545
Commercial | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									367
Industrial | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									729
Industrial | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									674
Industrial | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									55
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									92
Other | Enterprises | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									92
Other | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									436
Other | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									260
Other | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers									$ 176