Regulatory Matters (Schedule Of The Components Of Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Regulatory Matters [Line Items]
Regulatory assets, current		$ 16	$ 89
Regulatory assets, noncurrent		1,840	1,956
Regulatory liabilities, current		82	67
Regulatory liabilities, noncurrent		2,088	2,095
Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory assets, current		16	89
Regulatory assets, noncurrent		1,840	1,956
Total regulatory asset		1,856	2,045
Regulatory liabilities, current		82	67
Regulatory liabilities, noncurrent		2,088	2,095
Total regulatory liabilities		2,170	2,162
Cost Of Removal [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory liabilities, noncurrent		$ 1,745	1,673
Renewable Energy Plan [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Noncurrent Regulatory Liability, Recovery End Date		2028
Regulatory liabilities, noncurrent		$ 109	131
Income Taxes, Net [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Current Regulatory Liability Recovery End Date		2016
Regulatory liabilities, current		$ 64	64
Regulatory liabilities, noncurrent		64	103
ARO [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory liabilities, noncurrent		$ 73	83
Renewable Energy Grant [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Noncurrent Regulatory Liability, Recovery End Date		2043
Regulatory liabilities, noncurrent		$ 60	63
Energy Optimization Plan [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory liabilities, noncurrent		$ 26	32
Other Regulatory Assets [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Current Regulatory Liability Recovery End Date		2016
Regulatory liabilities, current		$ 4	3
Regulatory liabilities, noncurrent		11	10
Postretirement Benefits [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory assets, noncurrent	[1]	$ 1,096	1,195
Securitized Costs [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory Current Asset, End Date for Recovery	[2]	2015
Current Regulatory Liability Recovery End Date		2016
Regulatory assets, current	[2]		61
Regulatory liabilities, current		$ 14
Costs Of Electric Generating Units To Be Retired And Securitized [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Noncurrent Regulatory Asset Recovery End Date	[2]	2029
Regulatory assets, noncurrent	[2]	$ 348	370
Manufactured Gas Plant [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory assets, noncurrent	[3]	146	147
ARO [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory assets, noncurrent	[3]	151	139
Unamortized Debt Costs [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory assets, noncurrent	[3]	61	66
Gas Storage Inventory Adjustments [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory assets, noncurrent	[3]	$ 18	21
Energy Optimization Plan Incentive [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory Current Asset, End Date for Recovery	[4]	2016
Noncurrent Regulatory Asset Recovery End Date	[3],[4]	2017
Regulatory assets, current	[4]	$ 16	17
Regulatory assets, noncurrent	[3],[4]	$ 18	17
Major Maintenance [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory Current Asset, End Date for Recovery	[2]	2015
Regulatory assets, current	[2]		8
Other Regulatory Assets [Member] | Consumers Energy Company [Member]
Regulatory Matters [Line Items]
Regulatory Current Asset, End Date for Recovery	[2]	2015
Regulatory assets, current	[2]		3
Regulatory assets, noncurrent		$ 2	$ 1

[1] This regulatory asset is offset partially by liabilities. The net amount is included in rate base, thereby providing a return.

[2] These regulatory assets are included in rate base (or are expected to be included, for costs incurred subsequent to the most recently approved rate case), thereby providing a return on expenditures, or provide a specific return on investment authorized by the MPSC.

[3] These regulatory assets represent incurred costs for which the MPSC has provided, or Consumers expects, recovery without a return on investment.

[4] These regulatory assets have arisen from alternative revenue programs and are not associated with incurred costs or capital investments. Therefore, the MPSC has provided for recovery without a return.