Plant, Property, and Equipment (Plant, Property, and Equipment Table) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Public Utility, Property, Plant and Equipment [Line Items]
Construction work in progress		$ 1,509	$ 1,106
Less accumulated depreciation and amortization		(5,747)	(5,415)
Total plant, property, and equipment	[1]	14,705	13,412
Public Utilities, Property Plant and Equipment Additions		1,400	1,600
Public Utilities, Property Plant and Equipment Disposals		187	126
Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Construction work in progress		1,467	1,103
Less accumulated depreciation and amortization		(5,676)	(5,346)
Total plant, property, and equipment	[1]	14,588	13,337
Public Utilities, Property Plant and Equipment Additions		1,400	1,600
Public Utilities, Property Plant and Equipment Disposals		187	126
Electricity Generation Plant, Non-Nuclear [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing		$ 4,925	4,544
Electricity Generation Plant, Non-Nuclear [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] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Generation		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		$ 4,925	4,544
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]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution		$ 6,809	6,487
Electric Distribution [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		20 years
Electric Distribution [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		75 years
Electric Distribution [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution		$ 6,809	6,487
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 Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment		$ 1,039	910
Electric Other [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		5 years
Electric Other [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		50 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		$ 1,039	910
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]
Public Utility, Property, Plant and Equipment [Line Items]
Capital leases and financing obligation		$ 286	289
Electric Capital Leases [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Capital leases and financing obligation		286	289
Gas Distribution [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution		$ 3,497	3,239
Gas Distribution [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		28 years
Gas Distribution [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		80 years
Gas Distribution [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution		$ 3,497	3,239
Gas Distribution [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		28 years
Gas Distribution [Member] | Consumers Energy Company [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Distribution		80 years
Gas Transmission [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Transmission		$ 981	974
Gas Transmission [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Transmission		17 years
Gas Transmission [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Transmission		75 years
Gas Transmission [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Transmission		$ 981	974
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]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	[2]	$ 601	578
Gas Underground Storage Facilities [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other	[2]	29 years
Gas Underground Storage Facilities [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other	[2]	65 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	[2]	$ 601	578
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	[2]	29 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	[2]	65 years
Gas Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment		$ 630	538
Gas Other [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		5 years
Gas Other [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		50 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		$ 630	538
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]
Public Utility, Property, Plant and Equipment [Line Items]
Capital leases and financing obligation		$ 14	6
Gas Capital Leases [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Capital leases and financing obligation		14	6
Natural Gas [Member] | Gas Underground Storage Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment		26	26
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		$ 95	90
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		30 years
Enterprises Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Plant, property, and equipment, gross		$ 25	25
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		40 years
Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other non-utility property		$ 41	41
Other [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		2 years
Other [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		51 years
Other [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other non-utility property		$ 15	$ 15
Other [Member] | Consumers Energy Company [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Depreciable Life in Years, Other		8 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, 2015, utility plant additions were $1.4 billion and utility plant retirements were $187 million. For the year ended December 31, 2014, utility plant additions were $1.6 billion and utility plant retirements were $126 million.

[2] Underground storage includes base natural gas of $26 million at December 31, 2015 and 2014. Base natural gas is not subject to depreciation.