Related Party Transactions - Consumers (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Consumers Energy Company [Member]	Dec. 31, 2012 Consumers Energy Company [Member]	Dec. 31, 2011 Consumers Energy Company [Member]	Jan. 31, 2014 Consumers Energy Company [Member] Credit Agreement [Member]
Related Party Transaction [Line Items]
Purchased power - related parties	$ 90	$ 87	$ 82	$ 89	$ 86	$ 81
Accounts payable - related parties	10	9		13	11
Investment Owned, Balance, Shares				1.1
Investments				29	32
Maximum borrowing capacity							$ 300