Regulatory Matters (Schedule Of The Components Of Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current		$ 17	$ 16
Regulatory assets, noncurrent		2,091	1,840
Regulatory liabilities, current		95	82
Regulatory liabilities, noncurrent		2,041	2,088
Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current		17	16
Regulatory assets, noncurrent		2,091	1,840
Total regulatory asset		2,108	1,856
Regulatory liabilities, current		95	82
Regulatory liabilities, noncurrent		2,041	2,088
Total regulatory liabilities		2,136	2,170
Cost Of Removal [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, noncurrent		$ 1,809	1,745
Renewable Energy Plan [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Noncurrent Regulatory Liability, Recovery End Date		2028
Regulatory liabilities, noncurrent		$ 83	109
Income Taxes, Net [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Current Regulatory Liability Recovery End Date		2017
Regulatory liabilities, current		$ 64	64
Regulatory liabilities, noncurrent		7	64
ARO [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, noncurrent		$ 62	73
Renewable Energy Grant [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Noncurrent Regulatory Liability, Recovery End Date		2043
Regulatory liabilities, noncurrent		$ 58	60
Energy Optimization [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Noncurrent Regulatory Asset Recovery End Date		2018
Regulatory assets, noncurrent		$ 18	18
Regulatory liabilities, noncurrent		11	26
Other Regulatory Assets [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, noncurrent		$ 11	11
Revenue Subject To Refund [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Current Regulatory Liability Recovery End Date		2017
Regulatory liabilities, current		$ 31	18
Postretirement Benefits [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	[1]	$ 1,373	1,096
Securitized Costs [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Noncurrent Regulatory Asset Recovery End Date	[2]	2029
Regulatory assets, noncurrent	[2]	$ 323	348
Manufactured Gas Plant [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	[1]	139	146
ARO [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		166	151
Unamortized Loss On Reacquired Debt [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		54	61
Gas Storage Inventory Adjustments [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	[3]	$ 14	18
Energy Optimization [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Current Asset, End Date for Recovery	[4]	2017
Regulatory assets, current	[4]	$ 17	16
Other Regulatory Assets [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		$ 4	$ 2

[1] The MPSC has authorized a specific return on this regulatory asset.

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

[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 an alternative revenue program and are not associated with incurred costs or capital investments. Therefore, the MPSC has provided for recovery without a return.