Income Taxes (Schedule Of Effective Income Rate Reconciliation) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Income from continuing operations before income taxes		$ 829	$ 774	$ 886
Income tax expense at statutory rate		174	163	310
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect		48	46	26
TCJA excess deferred taxes		(31)	(26)	0
Production tax credits		(20)	(14)	(8)
Accelerated flow-through of regulatory tax benefits2		(13)	(39)	(39)
Research and development tax credits, net		(2)	(11)	(1)
Impact of the TCJA		0	(4)	148
Other, net		(9)	0	(12)
Tax expense		$ 147	$ 115	$ 424
Effective tax rate		17.70%	14.90%	47.90%
Income tax benefit				$ 14
Valuation allowance		$ 2	$ 8
Consumers Energy Company
Income Taxes [Line Items]
Income from continuing operations before income taxes		928	847	971
Income tax expense at statutory rate		195	178	340
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect		53	51	30
TCJA excess deferred taxes		(31)	(26)	0
Production tax credits		(12)	(12)	(8)
Accelerated flow-through of regulatory tax benefits2		(13)	(39)	(39)
Research and development tax credits, net		(2)	(11)	(1)
Impact of the TCJA		0	1	33
Other, net		(5)	0	(16)
Tax expense		$ 185	$ 142	$ 339
Effective tax rate		19.90%	16.80%	34.90%
Reduction of income tax expense				$ 14
Net regulatory tax liability		$ 3,829	$ 3,836
Plant, property, and equipment (subject to normalization) | Consumers Energy Company
Increase (decrease) in income taxes from:
Net regulatory tax liability				$ 1,600
Research Tax Credit Carryforward | Consumers Energy Company
Increase (decrease) in income taxes from:
Increase in tax credit carryforward	$ 8
Eliminate Write Off of Alternative Minimum Tax Credits
Increase (decrease) in income taxes from:
Valuation allowance			$ 9