Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Consumers Energy Company [Member]	Dec. 31, 2012 Consumers Energy Company [Member]	Jan. 31, 2013 Renewable Energy Grant [Member] Consumers Energy Company [Member]
Regulatory Liabilities [Line Items]
Proceeds from government grant	$ 69	$ 69		$ 69
Recorded liability		$ 2,282	$ 2,126	$ 69