Income Taxes (Loss And Credit Carryforwards) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Total tax attributes	$ 629
Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Total tax attributes	48
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	900
Federal net operating loss carryforward, Tax Attribute	315
Internal Revenue Service (IRS) [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	129
Federal net operating loss carryforward, Tax Attribute	45
Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	420
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	5
Charitable contribution carryover, Tax Attribute	2
Charitable Contribution Carryover [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	5
Charitable contribution carryover, Tax Attribute	2
General Business Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	37
General business credits, Tax Attribute	$ 37