Financings (Major Long-Term Debt Transactions) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended					9 Months Ended
	Sep. 30, 2011 Repayment of Debt [Member] Senior Notes 6.3% Due February 2012 [Member]	Sep. 30, 2011 Consumers Energy Company [Member] Debt Issuances [Member] April 2018 Tax-Exempt Bonds [Member]		Sep. 30, 2011 Consumers Energy Company [Member] Debt Issuances [Member] April 2035 Tax Exempt Bonds [Member]		Sep. 30, 2011 Debt Issuances [Member]	Sep. 30, 2011 Debt Issuances [Member] Senior Notes [Member]	Sep. 30, 2011 Consumers Energy Company [Member] Debt Retirements [Member] Nuclear Fuel Disposal Liability [Member]		Sep. 30, 2011 Consumers Energy Company [Member] Debt Retirements [Member] April 2018 Tax-Exempt Bonds [Member]		Sep. 30, 2011 Consumers Energy Company [Member] Debt Retirements [Member] April 2035 Tax Exempt Bonds [Member]		Sep. 30, 2011 Debt Retirements [Member]	Sep. 30, 2011 Debt Retirements [Member] Senior Notes [Member]	Sep. 30, 2011 Consumers Energy Company [Member] April 2018 Tax-Exempt Bonds [Member]	Sep. 30, 2011 Consumers Energy Company [Member] April 2035 Tax Exempt Bonds [Member]
Debt Issuance, Principal	$ 50	$ 68	[1]	$ 35	[1]	$ 353	$ 250
Interest Rate	6.30%						2.75%								8.50%	0.26%	0.28%
Debt Issuance Date		May 2011	[1]	May 2011	[1]		May 2011
Maturity Date	Feb. 01, 2012	Apr. 15, 2018		Apr. 01, 2035	[1]		May 15, 2014					Apr. 01, 2035	[2]		Apr. 15, 2011
Debt Retirement, Principal								$ 163	[2]	$ 68	[1]	$ 35	[2]	$ 412	$ 146
Debt Retirement Date								July 2011	[2]	May 2011	[1]	May 2011	[2]		April 2011

[1] 1 In May 2011, Consumers utilized the Michigan Strategic Fund for the issuance of $68 million and $35 million of tax-exempt Michigan Strategic Fund Variable Rate Limited Obligation Revenue Bonds. The initial interest rate, which resets weekly, was 0.26 percent for the $68 million bond issuance and 0.28 percent for the $35 million bond issuance. The bonds, which are backed by letters of credit and collateralized by FMBs, are subject to optional tender by the holders that would result in remarketing. Consumers used the proceeds to redeem $103 million of tax-exempt bonds in May 2011.

[2] 2 In July 2011, Consumers settled its nuclear fuel disposal liability with the DOE. For additional details, see the "Consumers' Electric Utility Contingencies — Nuclear Matters" section in Note 3, Contingencies and Commitments.