Consolidated Statements Of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating Revenue	$ 1,449	$ 1,371	$ 3,278	$ 3,172
Operating Expenses
Fuel for electric generation	125	97	242	222
Purchased and interchange power	373	365	706	711
Purchased power - related parties	21	21	43	43
Cost of gas sold	111	91	447	445
Maintenance and other operating expenses	315	286	605	589
Depreciation and amortization	197	176	459	414
General taxes	66	60	147	147
Total operating expenses	1,208	1,096	2,649	2,571
Operating Income	241	275	629	601
Other Income (Expense)
Interest income	2	2	7	3
Allowance for equity funds used during construction	2	3	4	6
Income from equity method investees	3	3	7	7
Nonoperating retirement benefits, net	4	10	7	20
Other income		2	2	5
Other expense	(2)	(4)	(4)	(7)
Total other income	9	16	23	34
Interest Charges
Interest on long-term debt	103	103	203	203
Other interest expense	8	7	16	14
Allowance for borrowed funds used during construction	(1)	(2)	(2)	(3)
Total interest charges	110	108	217	214
Income Before Income Taxes	140	183	435	421
Income Tax Expense	47	58	143	132
Net Income	93	125	292	289
Income Attributable to Noncontrolling Interests	1	1	1	1
Net Income Available to Common Stockholders	$ 92	$ 124	$ 291	$ 288
Basic Earnings Per Average Common Share	$ 0.33	$ 0.45	$ 1.04	$ 1.04
Diluted Earnings Per Average Common Share	0.33	0.45	1.04	1.04
Dividends Declared Per Common Share	$ 0.3325	$ 0.3100	$ 0.6650	$ 0.6200
Consumers Energy Company [Member]
Operating Revenue	$ 1,362	$ 1,293	$ 3,099	$ 3,016
Operating Expenses
Fuel for electric generation	100	73	189	172
Purchased and interchange power	369	360	700	703
Purchased power - related parties	22	21	44	43
Cost of gas sold	105	87	437	438
Maintenance and other operating expenses	285	264	550	542
Depreciation and amortization	195	173	455	410
General taxes	64	61	143	146
Total operating expenses	1,140	1,039	2,518	2,454
Operating Income	222	254	581	562
Other Income (Expense)
Interest income	2	1	6	2
Interest and dividend income - related parties		1		1
Allowance for equity funds used during construction	2	3	4	6
Nonoperating retirement benefits, net	2	10	5	19
Other income		2	14	5
Other expense	(2)	(4)	(4)	(7)
Total other income	4	13	25	26
Interest Charges
Interest on long-term debt	66	65	132	130
Other interest expense	4	3	7	6
Allowance for borrowed funds used during construction	(1)	(2)	(2)	(3)
Total interest charges	69	66	137	133
Income Before Income Taxes	157	201	469	455
Income Tax Expense	53	69	154	151
Net Income	104	132	315	304
Preferred Stock Dividends	1	1	1	1
Net Income (Loss) Available to Common Stockholders	$ 103	$ 131	$ 314	$ 303