Retirement Benefits (Schedule Of Plan Contributions) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	$ 229		$ 72		$ 323
Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	222		68		315
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	72	[1]	65	[1]
Estimated future employer contributions	75
OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	71	[1]	64	[1]
Estimated future employer contributions	74
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	150	[2]
Pension [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	147	[2]
VEBA Trust [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	55	[1]	45	[1]
VEBA Trust [Member] | OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	55	[1]	45	[1]
401 (h) Component [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	17	[1]	20	[1]
401 (h) Component [Member] | OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	$ 16	[1]	$ 19	[1]
Equity Securities [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	50.00%		50.00%
Equity Securities [Member] | OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	50.00%		50.00%
Equity Securities [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	50.00%		50.00%		50.00%
Equity Securities [Member] | Pension [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	50.00%		50.00%		50.00%
Fixed Income Funds [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	20.00%		20.00%
Fixed Income Funds [Member] | OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	20.00%		20.00%
Fixed Income Funds [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	30.00%		30.00%		30.00%
Fixed Income Funds [Member] | Pension [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	30.00%		30.00%		30.00%
Alternative Strategy Investments [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	30.00%		30.00%
Alternative Strategy Investments [Member] | OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	30.00%		30.00%
Alternative Strategy Investments [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	20.00%		20.00%		20.00%
Alternative Strategy Investments [Member] | Pension [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	20.00%		20.00%		20.00%

[1] CMS Energy, including Consumers, plans to contribute $75 million to the OPEB Plan in 2014, of which Consumers plans to contribute $74 million.

[2] CMS Energy, including Consumers, does not presently plan to contribute to the Pension Plan in 2014.