Income Taxes (Schedule Of Net Regulatory Tax Liability) (Details) - Consumers Energy Company [Member] - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Regulatory Liabilities		$ 3,795	$ 2,136
Net Regulatory Tax Liability [Member]
Income Taxes [Line Items]
Regulatory Liabilities		1,588
Plant, Property, And Equipment (Subject To Normalization) [Member]
Income Taxes [Line Items]
Regulatory Liabilities	[1]	1,781
All Other, Net (Not Subject To Normalization) [Member]
Income Taxes [Line Items]
Regulatory Liabilities	[1]	$ (193)

[1] Relates to deferred taxes arising from accelerated tax depreciation on assets in rate base that are governed by normalization provisions of the U.S. Internal Revenue Code. These normalization provisions generally require that customer rate refunds associated with changes in deferred taxes be returned to customers over the remaining average service life of the associated assets. Consumers will collect from customers the portion not subject to normalization over a period to be determined in a future regulatory proceeding. Consumers cannot predict the impact of orders from the MPSC related to the treatment of regulatory balances not subject to amortization.