Financial Instruments (Summary of the Sales Activity for Investment Securities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Proceeds from Sales of Available-for-Sale Securities	$ 3	$ 3	$ 29
Consumers Energy Company [Member]
Proceeds from Sales of Available-for-Sale Securities	$ 2	$ 2	$ 19