Plant, Property, and Equipment (Schedule of Finite-Lived Intangible Assets by Major Class Table) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	$ 930	$ 787
Finite-Lived Intangible Assets, Accumulated Amortization		368	293
Public Utilities, Property Plant and Equipment Additions		1,400	1,600
Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	925	785
Finite-Lived Intangible Assets, Accumulated Amortization		365	291
Public Utilities, Property Plant and Equipment Additions		1,400	1,600
Software and Software Development Costs [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	734	596
Finite-Lived Intangible Assets, Accumulated Amortization		294	223
Software and Software Development Costs [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	729	594
Finite-Lived Intangible Assets, Accumulated Amortization		291	221
Leasehold Improvements [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1],[2]	7	5
Finite-Lived Intangible Assets, Accumulated Amortization	[2]	5	4
Leasehold Improvements [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1],[2]	7	5
Finite-Lived Intangible Assets, Accumulated Amortization	[2]	5	4
Intangible Plant [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property Plant and Equipment Additions		140	96
Rights of Way [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	153	150
Finite-Lived Intangible Assets, Accumulated Amortization		46	44
Rights of Way [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	153	150
Finite-Lived Intangible Assets, Accumulated Amortization		46	44
Franchises and Consents [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	15	15
Finite-Lived Intangible Assets, Accumulated Amortization		8	8
Franchises and Consents [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	15	15
Finite-Lived Intangible Assets, Accumulated Amortization		8	8
Other Intangible Assets [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	21	21
Finite-Lived Intangible Assets, Accumulated Amortization		15	14
Other Intangible Assets [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Assets, Gross	[1]	21	21
Finite-Lived Intangible Assets, Accumulated Amortization		$ 15	$ 14
Minimum [Member] | Software and Software Development Costs [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		2 years
Minimum [Member] | Software and Software Development Costs [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		3 years
Minimum [Member] | Rights of Way [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		50 years
Minimum [Member] | Rights of Way [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		50 years
Minimum [Member] | Franchises and Consents [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Minimum [Member] | Franchises and Consents [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Maximum [Member] | Software and Software Development Costs [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		15 years
Maximum [Member] | Software and Software Development Costs [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		15 years
Maximum [Member] | Rights of Way [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		75 years
Maximum [Member] | Rights of Way [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		75 years
Maximum [Member] | Franchises and Consents [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		30 years
Maximum [Member] | Franchises and Consents [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life		30 years

[1] Net intangible asset additions for Consumers' utility plant were $140 million during 2015 and $96 million during 2014 and primarily represented software development costs.

[2] Leasehold improvements are amortized over the life of the lease, which may change whenever the lease is renewed or extended.