Financings And Capitalization (Major Long-Term Debt Transactions) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended					3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 CMS Energy [Member]	Sep. 30, 2014 Consumers Energy Company [Member]	Sep. 30, 2013 Consumers Energy Company [Member]	Sep. 30, 2014 Consumers Energy Company [Member] Other Paid-in Capital [Member]	Sep. 30, 2014 Consumers Energy Company [Member] Other Paid-in Capital [Member]	Sep. 30, 2014 Senior Notes 3.875% Due March 2024 [Member] CMS Energy [Member]		Sep. 30, 2014 Senior Notes 4.875% Due March 2044 [Member] CMS Energy [Member]		Sep. 30, 2014 Securitization Bonds 1.334% Due November 2020 [Member] Consumers Energy Company [Member]		Sep. 30, 2014 Securitization Bonds 2.962% Due November 2025 [Member] Consumers Energy Company [Member]		Sep. 30, 2014 Securitization Bonds 3.528% Due May 2029 [Member] Consumers Energy Company [Member]		Sep. 30, 2014 FMB's 3.125% Due August 2024 [Member] Consumers Energy Company [Member]	Sep. 30, 2014 FMB's 4.350% Due August 2064 [Member] Consumers Energy Company [Member]	Sep. 30, 2014 Senior Notes 6.875% Due December 2015 [Member] CMS Energy [Member]		Sep. 30, 2014 Senior Notes 5.500% Due June 2029 [Member] CMS Energy [Member]	Sep. 30, 2014 FMB's 5.500% Due August 2016 [Member] Consumers Energy Company [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt	$ 1,428	$ 1,025	$ 550	$ 878	$ 750			$ 250	[1]	$ 300	[1]	$ 124	[2]	$ 139	[2]	$ 115	[2]	$ 250	$ 250
Debt retirement, principal	457		280	177																125	[3]	155	177
Interest rate								3.875%	[1]	4.875%	[1]	1.334%	[2]	2.962%	[2]	3.528%	[2]	3.125%	4.35%	6.875%	[3]	5.50%	5.50%
Debt issuance date								February 2014	[1]	February 2014	[1]	July 2014	[2]	July 2014	[2]	July 2014	[2]	August 2014	August 2014
Debt retirement date																				April 2014	[3]	June 2014	August 2014
Maturity date								March 2024	[1]	March 2044	[1]	November 2020	[2]	November 2025	[2]	May 2029	[2]	August 2024	August 2064	December 2015	[3]	June 2029	August 2016
Adjustments to Additional Paid in Capital, Return of stockholder contribution						178	178
Loss on extinguishment of debt																				$ 13

[1] CMS Energy used a portion of these proceeds to retire its $125 million 6.875 percent senior notes due December 2015 and its $155 million 5.5 percent convertible senior notes due June 2029. CMS Energy intends to use the remaining proceeds for general corporate purposes.

[2] These Securitization bonds are collateralized by certain regulatory assets held by Consumers 2014 Securitization Funding. The bondholders have no recourse to Consumers’ other assets. Through its rate structure, Consumers collects from its retail electric customers, with some exceptions, Securitization charges to cover the principal and interest on the bonds as well as certain other qualified costs. The surcharges collected are remitted to a trustee and are not available to creditors of Consumers or creditors of Consumers’ affiliates other than Consumers 2014 Securitization Funding. Consumers used the proceeds from the Securitization property to retire $177 million of its 5.5 percent FMBs due August 2016 and $178 million of its equity. For additional details regarding the Securitization, see Note 2, Regulatory Matters.

[3] CMS Energy retired this debt at a premium and recorded a loss on extinguishment of $13 million in other expense on its consolidated statements of income.