Plant, Property, and Equipment (Schedule of Finite Lived Intangible Assets Amortization Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Finite-Lived Intangible Assets, Amortization Expense	$ 32	$ 28	$ 30
Consumers Energy Company [Member]
Finite-Lived Intangible Assets, Amortization Expense	32	27	30
Software and Software Development Costs [Member]
Finite-Lived Intangible Assets, Amortization Expense	24	19	22
Software and Software Development Costs [Member] | Consumers Energy Company [Member]
Finite-Lived Intangible Assets, Amortization Expense	24	19	22
Minimum [Member]
Finite-Lived Intangible Assets, Future Amortization Expense	39
Minimum [Member] | Consumers Energy Company [Member]
Finite-Lived Intangible Assets, Future Amortization Expense	39
Maximum [Member]
Finite-Lived Intangible Assets, Future Amortization Expense	50
Maximum [Member] | Consumers Energy Company [Member]
Finite-Lived Intangible Assets, Future Amortization Expense	$ 50