Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for uncollectible accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 20	$ 20	$ 24
Charged to Expense	29	29	29
Charged to Other Accounts	0	0	0
Deductions	29	29	33
Balance at End of Period	20	20	20
Allowance for uncollectible accounts | Consumers Energy Company
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	20	20	24
Charged to Expense	29	29	29
Charged to Other Accounts	0	0	0
Deductions	29	29	33
Balance at End of Period	20	20	20
Deferred tax valuation allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	8	15	5
Charged to Expense	0	2	10
Charged to Other Accounts	0	0	0
Deductions	6	9	0
Balance at End of Period	2	8	15
Allowance for notes receivable
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	24	20	16
Charged to Expense	38	25	20
Charged to Other Accounts	0	0	0
Deductions	29	21	16
Balance at End of Period	$ 33	$ 24	$ 20