Regulatory Matters - (Narrative) (Details) $ in Millions	1 Months Ended				12 Months Ended
	Aug. 31, 2023 USD ($)	Jan. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2023 USD ($) facility	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2016 unit	Dec. 31, 2015 unit	Dec. 31, 2013 USD ($)	Nov. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)
Public Utilities, General Disclosures [Line Items]
Incentive revenue					$ 7,462		$ 8,596		$ 7,329
Regulatory assets			$ 3,595		3,683		3,595
Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Incentive revenue					7,166		8,151		7,021
Regulatory assets			3,595		3,683		3,595
Regulatory liability			3,900		3,950		3,900
Purchased and interchange power					1,331		1,867		1,599
Cost of gas sold					897		1,243		726
Consumers Energy Company | Voluntary refund mechanism
Public Utilities, General Disclosures [Line Items]
Regulatory liability			22				22
Consumers Energy Company | Reserve for customer refunds
Public Utilities, General Disclosures [Line Items]
Regulatory liability					15
Consumers Energy Company | Contributions to assistance programs
Public Utilities, General Disclosures [Line Items]
Regulatory liability					$ 10
Consumers Energy Company | Renewable energy grant
Public Utilities, General Disclosures [Line Items]
Proceeds from government grant												$ 69
Consumers Energy Company | MGP sites
Public Utilities, General Disclosures [Line Items]
Number of former MGPs | facility					23
Regulatory asset collection period					10 years
Consumers Energy Company | Gas-Fueled Electric Generation
Public Utilities, General Disclosures [Line Items]
Number of units retired | unit											3
Consumers Energy Company | Coal-Fueled Electric Generation
Public Utilities, General Disclosures [Line Items]
Number of units retired | unit										7
Consumers Energy Company | J.H. Campbell Generating Units
Public Utilities, General Disclosures [Line Items]
Regulatory assets				$ 1,300
Rate of return on equity authorized				9.00%
PSCR underrecoveries | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
PSCR underrecoveries			401		$ 0		401
Purchased and interchange power							2,500		$ 2,100
Over (under) recovery for gas fuel and power supply costs authorized														$ 7
Over (under) recovery for gas fuel and power supply costs requested						$ (404)
PSCR underrecoveries | Consumers Energy Company | Revision of Prior Period, Adjustment
Public Utilities, General Disclosures [Line Items]
Over (under) recovery for gas fuel and power supply costs requested													$ (401)
Energy Waste Reduction Plan Incentive | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Authorized recovery collection													$ 55
Incentive revenue					58		$ 55
Regulatory assets					$ 58
Electric Rate Case | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Rate of return on equity authorized		9.90%
Additional annual rate increase authorized		$ 155
Surcharge for the recovery of excess distribution investments		$ 6
Gas Rate Case | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Rate of return on equity authorized	9.90%
Additional annual rate increase authorized	$ 95
Requested annual rate increase			$ 212
Requested annual rate increase, as a percent			10.25%
GCR underrecoveries | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Over (under) recovery for gas fuel and power supply costs authorized						(9)
Over (under) recovery for gas fuel and power supply costs requested															$ (15)
Cost of gas sold						$ 1,100		$ 700