Income Taxes (Loss And Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Operating Loss Carryforwards [Line Items]
Total tax attributes	$ 657
Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Total tax attributes	46
Federal Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	885
Federal net operating loss carryforward, Tax Attribute	311
Federal Tax Authority [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	121
Federal net operating loss carryforward, Tax Attribute	42
Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, Gross Amount	414
Local net operating loss carryforwards, Tax Attribute	4
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	2
Charitable contribution carryover, Tax Attribute	1
Charitable Contribution Carryover [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Charitable contribution carryforwards	2
Charitable contribution carryover, Tax Attribute	1
General Business Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	71
General business credits, Tax Attribute	71
Valuation Allowance - Loss carryforward	3
General Business Tax Credit Carryforward [Member] | Consumers Energy Company [Member]
Operating Loss Carryforwards [Line Items]
Tax credits, Gross Amount	3
General business credits, Tax Attribute	$ 3