Contingencies And Commitments (Contingencies And Commitments) (Details) violation in Thousands		1 Months Ended	12 Months Ended
	Jan. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) violation	Dec. 31, 2019 USD ($) site lawsuit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Regulatory assets			$ 2,489,000,000	$ 1,743,000,000
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets			2,489,000,000	1,743,000,000
Cost of gas sold			754,000,000	819,000,000	$ 730,000,000
Plant additions			2,000,000,000.0	1,800,000,000
Regulatory liability			3,829,000,000	$ 3,836,000,000
Bay Harbor
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 46,000,000
Discounted projected costs rate			4.34%
Accrual for environmental loss contingencies, inflation rate			1.00%
Remaining undiscounted obligation amount			$ 58,000,000
CERCLA Liability | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3,000,000
CERCLA Liability | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3,000,000
CERCLA Liability | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			8,000,000
Manufactured Gas Plant | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 68,000,000
Discounted projected costs rate			2.57%
Accrual for environmental loss contingencies, inflation rate			2.50%
Remaining undiscounted obligation amount			$ 73,000,000
Number of former MGPs | site			23
Regulatory asset collection period			10 years
Regulatory assets			$ 130,000,000
Electric Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3,000,000
Electric Utility | NREPA | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3,000,000
Electric Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			4,000,000
Gas Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			1,000,000
Gas Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3,000,000
Equatorial Guinea Tax Claim
Loss Contingencies [Line Items]
Foreign government tax claim on sale			$ 152,000,000
Class Action Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit			4
Individual Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit			1
Gas Index Price Reporting Litigation
Loss Contingencies [Line Items]
Estimated current litigation liability			$ 30,000,000
MCV PPA | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			270,000,000
Underwater cables Straits of Mackinac | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			5,000,000
Underwater cables Straits of Mackinac | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			10,000,000
MPSC Gas Staking MISS DIG Act | Consumers Energy Company
Loss Contingencies [Line Items]
Number of alleged violations | violation		20
Maximum possible loss per violation		$ 5,000
MPSC Gas Staking MISS DIG Act | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Expected settlement			1,000,000
Ray Compressor Station | Consumers Energy Company
Loss Contingencies [Line Items]
Cost of gas sold	$ 7,000,000
Plant additions			$ 12,000,000