Financings and Capitalization (Major Long-Term Debt Transactions) (Details) (USD $)				12 Months Ended			12 Months Ended						12 Months Ended					12 Months Ended								12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Debt Issuances [Member]	Dec. 31, 2011 Debt Retirements [Member]	Dec. 31, 2011 Term Loan $180 Million [Member]	Dec. 15, 2011 Term Loan $180 Million [Member]	Dec. 31, 2011 Senior Notes 2.75% Due May 2014 [Member] Debt Issuances [Member]	Dec. 31, 2011 Senior Notes 8.5% Due April 2011 [Member] Debt Retirements [Member]	Dec. 31, 2011 Senior Notes 6.3% Due February 2012 [Member] Debt Retirements [Member]	Dec. 31, 2011 Senior Notes 2.875% Due December 2024 [Member] Debt Retirements [Member]		Dec. 31, 2011 April 2018 Tax-Exempt Bonds [Member] Consumers Energy Company [Member]	Dec. 31, 2011 April 2018 Tax-Exempt Bonds [Member] Debt Issuances [Member] Consumers Energy Company [Member]		Dec. 31, 2011 April 2018 Tax-Exempt Bonds [Member] Debt Retirements [Member] Consumers Energy Company [Member]		Dec. 31, 2011 April 2035 Tax Exempt Bonds [Member] Consumers Energy Company [Member]	Dec. 31, 2011 April 2035 Tax Exempt Bonds [Member] Debt Issuances [Member] Consumers Energy Company [Member]		Dec. 31, 2011 April 2035 Tax Exempt Bonds [Member] Debt Retirements [Member] Consumers Energy Company [Member]		Dec. 31, 2011 Nuclear Fuel Disposal Liability [Member] Debt Retirements [Member] Consumers Energy Company [Member]		Dec. 31, 2011 Tax Exempt Bonds [Member] Debt Retirements [Member] Consumers Energy Company [Member]	Dec. 31, 2011 Trust Preferred Securities [Member]	Dec. 31, 2011 Trust Preferred Securities [Member] Repayment of Debt [Member]
Debt Issuance, Principal	$ 7,093,000,000	$ 7,206,000,000	$ 353,000,000				$ 250,000,000						$ 68,000,000	[1]				$ 35,000,000	[1]						$ 29,000,000
Interest Rate							2.75%	8.50%	6.30%	2.875%	[2]	0.26%					0.28%									7.75%
Debt Issuance Date							May 2011						May 2011	[1]				May 2011	[1]
Maturity Date							May 2014	April 2011	February 2012	December 2024	[2]		April 2018	[1]	April 2018	[1]		April 2035	[1]	April 2035	[1]	-	[3]
Debt Retirement, Principal				524,000,000				146,000,000	50,000,000	62,000,000	[2]				68,000,000	[1]				35,000,000	[1]	163,000,000	[3]	103,000,000
Debt Retirement Date								April 2011	October 2011						May 2011	[1]				May 2011	[1]	July 2011	[3]			February 2012
Conversion Date										December 2011	[2]
Term loan credit agreement						$ 180,000,000
LIBOR plus	2.00%				2.50%
Debt Instrument Call Date																										January 2012

[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] CMS Energy's contingently convertible notes. See the "Contingently Convertible Securities" section in this Note for further discussion of the conversions.

[3] 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 5, Contingencies and Commitments.