Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Uncollectible Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	[1]	$ 28	$ 40	$ 33
Charged to Expense	[1]	31	50	72
Charged to other Accounts	[1]
Deductions	[1]	35	62	65
Balance at End of Period	[1]	24	28	40
Allowance for Uncollectible Accounts [Member] | Consumers Energy Company [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		28	39	31
Charged to Expense		31	50	72
Charged to other Accounts
Deductions		35	61	64
Balance at End of Period		24	28	39
Deferred Tax Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		4	2	2
Charged to Expense		1	3
Charged to other Accounts			(1)
Deductions
Balance at End of Period		5	4	2
Deferred Tax Valuation Allowance [Member] | Consumers Energy Company [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period			1	1
Charged to Expense
Charged to other Accounts			(1)
Deductions
Balance at End of Period				1
Allowance For Notes Receivable [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	[1]	9	8	5
Charged to Expense	[1]	19	8	8
Charged to other Accounts	[1]
Deductions	[1]	12	7	5
Balance at End of Period	[1]	$ 16	$ 9	$ 8

[1] Deductions are write-offs of uncollectible accounts, net of recoveries.