Regulatory Matters (Narrative) (Details) $ in Millions	1 Months Ended			3 Months Ended								12 Months Ended
	Dec. 31, 2021 USD ($) coal_fueled_electric_generating_unit site	Jul. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) coal_fueled_electric_generating_unit site	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($) coal_fueled_electric_generating_unit site	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2016 site	Dec. 31, 2015 site	Dec. 31, 2013 USD ($)	Jan. 31, 2022 USD ($)	Oct. 31, 2021 USD ($)
Public Utilities, General Disclosures [Line Items]
Revenue				$ 2,033	$ 1,725	$ 1,558	$ 2,013	$ 1,727	$ 1,507	$ 1,382	$ 1,802	$ 7,329		$ 6,418		$ 6,624
Regulatory liabilities, current	$ 146			146				151				146		151
Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Revenue												$ 7,021		6,189		6,376
Number of units retired | site												10
Regulatory liabilities, current	$ 146			$ 146				151				$ 146		151
Reduction in depreciation expense												1,077		1,023		975
Plant additions												2,400		2,000
Purchased and interchange power												1,599		1,454		1,470
Cost of gas sold												$ 726		568		754
Costs of coal-fueled electric generating units to be retired | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Number Of Units | coal_fueled_electric_generating_unit	2			2								2
Coal-Fueled Electric Generation | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Number of units retired | site																	7
Gas-Fueled Electric Generation | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Number of units retired | site																		3
Energy Waste Reduction Plan Incentive | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Authorized recovery collection																					$ 42
Revenue												$ 46		42
Requested recovery/collection	$ 46			$ 46								46
Electric Rate Case | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Annual rate increase requested			$ 225
Rate of return on equity requested			10.50%
Annual rate increase requested, amended		$ 201
Annual rate increase authorized	$ 27
Rate of return on equity authorized	9.90%
Reduction in depreciation expense	$ (27)
Impairment charge	4											41
Assessment of probable loss	11			11								11
Plant additions												$ 23
Held-for-sale fleet assets	15
Electric Rate Case | Consumers Energy Company | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Recommended disallowed costs																				$ 11
PSCR overrecoveries/underrecoveries | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Purchased and interchange power														1,800		1,900
Over (under) recovery authorized by the MPSC								(4)						(4)		$ 18
GCR underrecoveries | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Over (under) recovery authorized by the MPSC			$ 1				$ 1				$ 6		$ 1		$ 6
Cost of gas sold													$ 400		$ 500
Renewable energy grant | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Proceeds from government grant																			$ 69
Income Taxes Subject To Normalization | Gas Rate Case Tax Reform Rate Change | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability remaining book life												44 years
Income Taxes Subject To Normalization | Electric Rate Case Tax Reform Rate Change | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability remaining book life												27 years
Reserve for customer refunds | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	2			2				28				$ 2		28
Voluntary transmission asset sale gain share | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	$ 0			$ 0				$ 14				$ 0		$ 14
Manufactured Gas Plant | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Number of former MGPs | site	23			23								23
Regulatory asset collection period												10 years