Regulatory Matters (Schedule Of The Components Of Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current		$ 20	$ 17
Regulatory assets, noncurrent		1,764	2,091
Regulatory liabilities, current		80	95
Regulatory liabilities, noncurrent		3,715	2,041
Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current		20	17
Regulatory assets, noncurrent		1,764	2,091
Total regulatory asset		1,784	2,108
Regulatory liabilities, current		80	95
Regulatory liabilities, noncurrent		3,715	2,041
Total regulatory liabilities		3,795	2,136
Cost Of Removal [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, noncurrent		$ 1,844	1,809
Income Taxes, Net [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Current Regulatory Liability Recovery End Date		2018
Regulatory liabilities, current		$ 52	64
Regulatory liabilities, noncurrent		1,564	7
Postretirement Benefits [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, noncurrent		$ 135
Renewable Energy Plan [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Noncurrent Regulatory Liability, Recovery End Date		2028
Regulatory liabilities, noncurrent		$ 56	83
Renewable Energy Grant [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Noncurrent Regulatory Liability, Recovery End Date		2043
Regulatory liabilities, noncurrent		$ 56	58
ARO [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, noncurrent		$ 50	62
Energy Waste Reduction Plan [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, noncurrent			11
Other Regulatory Asset (Liability) [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Current Regulatory Liability Recovery End Date		2018
Regulatory liabilities, current		$ 28	31
Regulatory liabilities, noncurrent		10	11
Postretirement Benefits [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	[1]	$ 1,028	1,373
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]	$ 298	323
ARO [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	[1]	161	166
Manufactured Gas Plant [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		142	139
Unamortized Loss On Reacquired Debt [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		53	54
Energy Waste Reduction Plan [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		$ 39	1
Energy Waste Reduction Plan Incentive [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Current Asset, End Date for Recovery	[3]	2018
Noncurrent Regulatory Asset Recovery End Date		2019
Regulatory assets, current	[3]	$ 18	17
Regulatory assets, noncurrent		31	18
Gas Storage Inventory Adjustments [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	[4]	$ 10	14
Other Regulatory Asset (Liability) [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Current Asset, End Date for Recovery		2018
Regulatory assets, current		$ 2
Regulatory assets, noncurrent		$ 2	$ 3

[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 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.

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