Plant, Property, and Equipment (Schedule Of Plant, Property, and Equipment) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Public Utility, Property, Plant and Equipment [Line Items]
Plant, property, and equipment, gross		$ 22,506	$ 21,010	$ 18,943
Construction work in progress		765	761
Accumulated depreciation and amortization		(6,510)	(6,056)
Total plant, property, and equipment	[1]	16,761	15,715
Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Plant, property, and equipment, gross		22,318	20,838	$ 18,797
Construction work in progress		753	759
Less accumulated depreciation and amortization		(6,441)	(5,994)
Total plant, property, and equipment	[1]	16,630	15,603
Public Utilities, Property Plant and Equipment Additions		1,700	2,300
Public Utilities, Property Plant and Equipment Disposals		$ 214	285
Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Consumers		3 years
Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Consumers		125 years
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing		$ 6,025	5,900
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Generation		22 years
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Generation		125 years
Electric Distribution [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution		$ 7,603	7,149
Electric Distribution [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		20 years
Electric Distribution [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		75 years
Electric Transmission [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Transmission		$ 66	59
Electric Transmission [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Transmission		46 years
Electric Transmission [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Transmission		75 years
Electric Other [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment		$ 1,229	1,137
Electric Other [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		5 years
Electric Other [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		50 years
Electric Capital Leases [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Capital leases and financing obligation	[1],[2]	$ 298	295
Gas Distribution [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution		$ 4,182	3,806
Gas Distribution [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		20 years
Gas Distribution [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		85 years
Gas Transmission [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Transmission		$ 1,278	1,124
Gas Transmission [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Transmission		17 years
Gas Transmission [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Transmission		75 years
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	[3]	$ 842	630
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other	[3]	27 years
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other	[3]	75 years
Gas Other [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment		$ 764	708
Gas Other [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		5 years
Gas Other [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		50 years
Gas Capital Leases [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Capital leases and financing obligation	[2]	$ 14	15
Natural Gas [Member] | Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment		26	26
Enterprises IPP [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Plant, property, and equipment, gross		$ 163	141
Enterprises IPP [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		3 years
Enterprises IPP [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		35 years
Enterprises Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Plant, property, and equipment, gross		$ 4	16
Enterprises Other [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		3 years
Enterprises Other [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		5 years
Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other non-utility property		$ 21	15
Other [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		1 year
Other [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		7 years
Other [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other non-utility property		$ 17	$ 15
Other [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		3 years
Other [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		51 years

[1] For the year ended December 31, 2017, Consumers' plant additions were $1.7 billion and plant retirements were $214 million. For the year ended December 31, 2016, Consumers' plant additions were $2.3 billion and plant retirements were $285 million.

[2] For information regarding the amortization terms of Consumers' assets under capital leases and financing obligation, see Note 10, Leases and Palisades Financing.

[3] Underground storage includes base natural gas of $26 million at December 31, 2017 and 2016. Base natural gas is not subject to depreciation.