Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities
Net income	$ 553	$ 525	$ 479
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	811	750	685
Deferred income taxes and investment tax credit	264	247	227
Bad debt expense	50	58	80
Other non-cash operating activities and reconciling adjustments	52	100	58
Postretirement benefits contributions	(108)	(262)	(32)
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	(155)	120	(31)
Decrease (increase) in inventories	146	147	(36)
Increase (decrease) in accounts payable and accrued refunds	59	(26)	50
Other current and non-current assets and liabilities	(43)	(19)	1
Net cash provided by operating activities	1,629	1,640	1,481
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,672)	(1,564)	(1,577)
Jackson plant acquisition		(154)
Increase in EnerBank notes receivable	(136)	(279)	(255)
Proceeds from the sale of EnerBank notes receivable		48
Cost to retire property and other investing activities	(107)	(115)	(66)
Net cash used in investing activities	(1,915)	(2,064)	(1,898)
Cash Flows from Financing Activities
Proceeds from issuance of debt	1,049	599	1,428
Proceeds from EnerBank certificates of deposit, net	100	214	233
Issuance of common stock	72	43	43
Retirement of long-term debt	(728)	(224)	(750)
Debt prepayment costs	(18)		(36)
Payment of dividends on common and preferred stock	(347)	(322)	(295)
Increase (decrease) in notes payable	149	189	(110)
Payment of capital lease obligations and other financing costs	(22)	(36)	(51)
Net cash provided by (used in) financing activities	255	463	462
Net Increase (Decrease in Cash and Cash Equivalents, Including Restricted Amounts	(31)	39	45
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	288	249	204
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	257	288	249
Cash transactions
Interest paid (net of amounts capitalized)	427	386	380
Income taxes paid (refunds received), net	32	10	22
Non-cash transactions
Capital expenditures not paid	138	201	201
Note receivable recorded for future refund of use taxes paid and capitalized	29
Other assets placed under capital lease	13	17	7
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	616	594	567
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	803	744	678
Deferred income taxes and investment tax credit	289	204	263
Bad debt expense	31	50	72
Other non-cash operating activities and reconciling adjustments	25	98	34
Postretirement benefits contributions	(98)	(243)	(29)
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	(138)	104	(16)
Decrease (increase) in inventories	145	144	(36)
Increase (decrease) in accounts payable and accrued refunds	57	(22)	47
Other current and non-current assets and liabilities	(49)	121	(226)
Net cash provided by operating activities	1,681	1,794	1,354
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,656)	(1,537)	(1,573)
Jackson plant acquisition		(154)
Cost to retire property and other investing activities	(112)	(110)	(70)
Net cash used in investing activities	(1,768)	(1,801)	(1,643)
Cash Flows from Financing Activities
Proceeds from issuance of debt	446	250	878
Retirement of long-term debt	(198)	(124)	(220)
Debt prepayment costs			(16)
Payment of dividends on common and preferred stock	(501)	(476)	(459)
Stockholder contribution	275	150	495
Increase (decrease) in notes payable	149	189	(110)
Return of stockholder contribution			(178)
Payment of capital lease obligations and other financing costs	(3)	(23)	(38)
Net cash provided by (used in) financing activities	168	(34)	352
Net Increase (Decrease in Cash and Cash Equivalents, Including Restricted Amounts	81	(41)	63
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	71	112	49
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	152	71	112
Cash transactions
Interest paid (net of amounts capitalized)	256	245	233
Income taxes paid (refunds received), net	50	(84)	266
Non-cash transactions
Capital expenditures not paid	127	182	201
Note receivable recorded for future refund of use taxes paid and capitalized	29
Other assets placed under capital lease	$ 13	$ 17	$ 7