Consolidated Statements Of Income - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Revenue		$ 6,583	$ 6,399	$ 6,456
Operating Expenses
Fuel for electric generation		505	499	593
Purchased and interchange power		1,503	1,508	1,406
Purchased power - related parties		86	86	83
Cost of gas sold		750	710	961
Maintenance and other operating expenses		1,236	1,248	1,223
Depreciation and amortization		881	811	750
General taxes		284	281	262
Total operating expenses		5,245	5,143	5,278
Operating Income		1,338	1,256	1,178
Other Income (Expense)
Interest income		12	6	12
Allowance for equity funds used during construction		5	12	10
Income from equity method investees	[1]	15	13	14
Nonoperating retirement benefits, net		24	41	(15)
Other income		6	8	10
Other expense		(76)	(75)	(17)
Total other income (expense)		(14)	5	14
Interest Charges
Interest on long-term debt		406	411	386
Other interest expense		34	29	14
Allowance for borrowed funds used during construction		(2)	(5)	(4)
Total interest charges		438	435	396
Income Before Income Taxes		886	826	796
Income Tax Expense		424	273	271
Net Income		462	553	525
Income Attributable to Noncontrolling Interests		2	2	2
Net Income Available to Common Stockholders		$ 460	$ 551	$ 523
Basic Earnings Per Average Common Share		$ 1.64	$ 1.99	$ 1.90
Diluted Earnings Per Average Common Share		$ 1.64	$ 1.98	$ 1.89
Consumers Energy Company [Member]
Operating Revenue		$ 6,222	$ 6,064	$ 6,165
Operating Expenses
Fuel for electric generation		398	393	497
Purchased and interchange power		1,491	1,486	1,376
Purchased power - related parties		90	88	83
Cost of gas sold		730	693	939
Maintenance and other operating expenses		1,113	1,127	1,132
Depreciation and amortization		872	803	744
General taxes		276	277	255
Total operating expenses		4,970	4,867	5,026
Operating Income		1,252	1,197	1,139
Other Income (Expense)
Interest income		9	4	11
Interest and dividend income - related parties		1	1	1
Allowance for equity funds used during construction		5	12	10
Nonoperating retirement benefits, net		21	37	(17)
Other income		17	8	19
Other expense		(58)	(55)	(17)
Total other income (expense)		(5)	7	7
Interest Charges
Interest on long-term debt		263	261	252
Other interest expense		15	12	2
Allowance for borrowed funds used during construction		(2)	(5)	(4)
Total interest charges		276	268	250
Income Before Income Taxes		971	936	896
Income Tax Expense		339	320	302
Net Income		632	616	594
Preferred Stock Dividends		2	2	2
Net Income Available to Common Stockholders		$ 630	$ 614	$ 592

[1] Consumers had no significant equity method investments.