Income Taxes (Loss And Credit Carryforwards) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Total tax attributes	$ 676
Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Total tax attributes	45
Federal Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	1,032
Federal net operating loss carryforward, Tax Attribute	362
Federal Tax Authority [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	125
Federal net operating loss carryforward, Tax Attribute	44
Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	406
Local net operating loss carryforwards, Tax Attribute	4
Valuation Allowance - Loss carryforward	1
State Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Capital loss carryforwards, Gross Amount	18
State capital loss carryforward, Tax Attribute	1
Valuation Allowance - Loss carryforward	1
State Jurisdiction [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Capital loss carryforwards, Gross Amount	10
State capital loss carryforward, Tax Attribute	1
Valuation Allowance - Loss carryforward	1
Alternative Minimum Tax [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	270
Alternative minimum tax credits, Tax Attribute	270
Charitable Contribution Carryover [Member]
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	1
Charitable contribution carryover, Tax Attribute	1
Charitable Contribution Carryover [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	1
General Business Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	38
General business credits, Tax Attribute	$ 38