Income Taxes (Loss And Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Operating Loss Carryforwards [Line Items]
General business credits	$ 206
Alternative minimum tax credits	29
Total tax attributes	239
Consumers Energy Company
Operating Loss Carryforwards [Line Items]
Total tax attributes	20
Local Tax Authority
Operating Loss Carryforwards [Line Items]
Local net operating loss carryforwards	389
Local net operating loss carryforwards	4
General business credits
Operating Loss Carryforwards [Line Items]
Tax credits	206
General business credits | Consumers Energy Company
Operating Loss Carryforwards [Line Items]
Tax credits	20
General business credits	20
Alternative minimum tax credits
Operating Loss Carryforwards [Line Items]
Tax credits	$ 29