Financings And Capitalization (Major Long-Term Debt Transactions) (Details) (CMS Energy [Member], USD $)	6 Months Ended
	Jun. 30, 2014
Debt Instrument [Line Items]
Debt issuance, principal	$ 550,000,000
Senior Notes 6.875% Due December 2015 [Member]
Debt Instrument [Line Items]
Debt retirement, principal	125,000,000
Interest rate	6.875%
Maturity date	December 2015
Loss on extinguishment of debt	13,000,000
Senior Notes 5.500% Due June 2029 [Member]
Debt Instrument [Line Items]
Debt retirement, principal	155,000,000
Interest rate	5.50%
Maturity date	June 2029
Debt Issuance [Member] | Senior Notes 3.875% Due March 2024 [Member]
Debt Instrument [Line Items]
Debt issuance, principal	250,000,000	[1]
Interest rate	3.875%	[1]
Debt issuance date	February 2014	[1]
Maturity date	March 2024	[1]
Debt Issuance [Member] | Senior Notes 4.875% Due March 2044 [Member]
Debt Instrument [Line Items]
Debt issuance, principal	300,000,000	[1]
Interest rate	4.875%	[1]
Debt issuance date	February 2014	[1]
Maturity date	March 2044	[1]
Debt Retirements [Member]
Debt Instrument [Line Items]
Debt retirement, principal	280,000,000
Debt Retirements [Member] | Senior Notes 6.875% Due December 2015 [Member]
Debt Instrument [Line Items]
Debt retirement, principal	125,000,000	[2]
Interest rate	6.875%	[2]
Debt retirement date	April 2014	[2]
Maturity date	December 2015	[2]
Debt Retirements [Member] | Senior Notes 5.500% Due June 2029 [Member]
Debt Instrument [Line Items]
Debt retirement, principal	$ 155,000,000
Interest rate	5.50%
Debt retirement date	June 2014
Maturity date	June 2029

[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] 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.