Income Taxes (Loss And Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
Total tax attributes	$ 871
Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Total tax attributes	190
Federal Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	1,415
Federal net operating loss carryforward, Tax Attribute	495
Federal Tax Authority [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	447
Federal net operating loss carryforward, Tax Attribute	157
Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	408
Local net operating loss carryforwards, Tax Attribute	4
Valuation Allowance - Loss carryforward	2
Alternative Minimum Tax [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	270
Alternative minimum tax credits, Tax Attribute	270
General Business Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	102
General business credits, Tax Attribute	102
Valuation Allowance - Loss carryforward	3
General Business Tax Credit Carryforward [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	33
General business credits, Tax Attribute	$ 33