Revenue (Components of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,962	$ 1,758
Leasing income	46	39
Financing income	75	67
Total operating revenue	2,083	1,864
Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,131	1,025
Financing income	3	3
Total operating revenue	1,134	1,028
Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	801	714
Financing income	2	2
Total operating revenue	803	716
Enterprises | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	30	19
Leasing income	46	39
Total operating revenue	76	58
Variable lease income	33	25
EnerBank | Operating Segments
Disaggregation of Revenue [Line Items]
Financing income	70	62
Total operating revenue	70	62
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,932	1,739
Financing income	5	5
Total operating revenue	1,937	1,744
Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,131	1,025
Financing income	3	3
Total operating revenue	1,134	1,028
Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	801	714
Financing income	2	2
Total operating revenue	803	716
Residential | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,122	974
Residential | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	568	481
Residential | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	554	493
Commercial | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	508	488
Commercial | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	345	339
Commercial | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	163	149
Industrial | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	161	160
Industrial | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	138	140
Industrial | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	23	20
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	30	19
Other | Enterprises | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	30	19
Other | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	141	117
Other | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	80	65
Other | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 61	$ 52