Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2017
Income Taxes [Line Items]
U.S. federal income tax rate		21.00%	21.00%
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect		4.60%	5.40%
TCJA excess deferred taxes		(3.90%)	(3.50%)
Research and development tax credits, net		(3.40%)	(0.20%)
AMT Sequestration		(3.30%)	0.00%
Production tax credits		(2.80%)	(2.40%)
Accelerated flow-through of regulatory tax benefits		(1.50%)	(1.50%)
Other, net		(0.70%)	(0.40%)
Effective tax rate		10.00%	18.40%
AMT sequestration income tax benefit	$ 9
Consumers Energy Company
Income Taxes [Line Items]
U.S. federal income tax rate		21.00%	21.00%
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect		4.90%	5.60%
TCJA excess deferred taxes		(3.40%)	(3.30%)
Research and development tax credits, net		(3.10%)	(0.20%)
Production tax credits		(1.40%)	(1.00%)
Accelerated flow-through of regulatory tax benefits		(1.90%)	(2.50%)
Other, net		(0.30%)	(0.30%)
Effective tax rate		15.80%	19.30%
Reduction of income tax expense		$ 5	$ 7
Research Tax Credit Carryforward
Increase (decrease) in income taxes from:
Increase in credit	9
Research Tax Credit Carryforward | Consumers Energy Company
Increase (decrease) in income taxes from:
Increase in credit	$ 8
Plant, Property, And Equipment (Subject To Normalization) | Consumers Energy Company
Increase (decrease) in income taxes from:
Regulatory liabilities				$ 1,600