Schedule II - Valuation and Qualifying Accounts and Reserves (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Uncollectible Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 33	$ 32	$ 35
Charged to Expense	72	63	53
Charged to other Accounts
Deductions	65	62	56
Balance at End of Period	40	33	32
Allowance for Uncollectible Accounts [Member] | Consumers Energy Company [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	31	30	33
Charged to Expense	72	63	53
Charged to other Accounts
Deductions	64	62	56
Balance at End of Period	39	31	30
Deferred Tax Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	2	3	20
Charged to other Accounts			(15)
Deductions		1	2
Balance at End of Period	2	2	3
Deferred Tax Valuation Allowance [Member] | Consumers Energy Company [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	1	1	1
Charged to Expense
Charged to other Accounts
Deductions
Balance at End of Period	1	1	1
Allowance For Notes Receivable [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	5	5	5
Charged to Expense	8	4	4
Charged to other Accounts
Deductions	5	4	4
Balance at End of Period	$ 8	$ 5	$ 5