Related Party Transactions - Consumers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Purchased power - related parties	$ 86	$ 83	$ 90
Accounts payable - related parties	12	9
Accounts receivable - related parties	12	11
Consumers Energy Company [Member]
Related Party Transaction [Line Items]
Purchased power - related parties	88	83	$ 89
Accounts payable - related parties	18	15
Accounts receivable - related parties	9	17
Due to related parties	24	23
Investments	33	$ 29
Future purchase power, related parties	4
Consumers Energy Company [Member] | Credit Agreement [Member]
Related Party Transaction [Line Items]
Maximum borrowing capacity	300
Amount outstanding	$ 0