Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	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		5.40%	5.90%
TCJA excess deferred taxes		(3.40%)	(3.40%)
Production tax credits		(2.50%)	(2.00%)
Accelerated flow-through of regulatory tax benefits		(1.50%)	(5.00%)
Research and development tax credits, net		(0.20%)	(1.60%)
Other, net		(1.20%)	0.20%
Effective tax rate		17.60%	15.10%
Regulatory liabilities, noncurrent		$ 3,754		$ 3,681
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		5.70%	6.10%
TCJA excess deferred taxes		(3.20%)	(3.10%)
Production tax credits		(1.60%)	(1.60%)
Accelerated flow-through of regulatory tax benefits		(1.00%)	(4.40%)
Research and development tax credits, net		(0.20%)	(1.50%)
Other, net		(0.40%)	(0.30%)
Effective tax rate		20.30%	16.20%
Regulatory liabilities, noncurrent		$ 3,754		$ 3,681
Reduction of income tax expense		7	$ 30
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					$ 1,800
TCJA Reserve For Refund | Consumers Energy Company
Increase (decrease) in income taxes from:
Regulatory liabilities, noncurrent		$ 62