Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities
Net income	$ 525	$ 479	$ 454
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	750	685	628
Deferred income taxes and investment tax credit	247	227	268
Postretirement benefits expense	91	23	144
Bad debt expense	58	80	67
Other non-cash operating activities	9	17	22
Postretirement benefits contributions	(262)	(32)	(229)
Proceeds from government grant			69
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	120	(31)	(120)
Decrease (increase) in inventories	147	(36)	202
Increase (decrease) in accounts payable and accrued refunds	(26)	50	4
Other current and non-current assets and liabilities	(19)	(15)	(88)
Net cash provided by operating activities	1,640	1,447	1,421
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,564)	(1,577)	(1,325)
Jackson plant acquisition	(154)
Cost to retire property	(89)	(75)	(56)
Increase in EnerBank notes receivable	(279)	(255)	(139)
Proceeds from the sale of EnerBank notes receivable	48
Other investing activities	(6)	(3)	(12)
Net cash used in investing activities	(2,044)	(1,910)	(1,532)
Cash Flows from Financing Activities
Proceeds from issuance of debt	599	1,428	1,025
Net increase in EnerBank certificates of deposit	214	233	125
Issuance of common stock	43	43	36
Retirement of long-term debt	(224)	(750)	(741)
Payment of dividends on common and preferred stock	(322)	(295)	(273)
Increase (decrease) in notes payable	189	(110)	60
Payment of capital lease obligations and other financing costs	(36)	(51)	(42)
Net cash provided by financing activities	463	498	190
Net Increase in Cash and Cash Equivalents	59	35	79
Cash and Cash Equivalents, Beginning of Period	207	172	93
Cash and Cash Equivalents, End of Period	266	207	172
Cash transactions
Interest paid (net of amounts capitalized)	386	380	382
Income taxes paid (refunds received), net	10	22	34
Non-Cash Transactions
Capital expenditures not paid	201	201	176
Other assets placed under capital lease	17	7	6
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	594	567	534
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	744	678	622
Deferred income taxes and investment tax credit	204	263	164
Postretirement benefits expense	90	24	142
Bad debt expense	50	72	63
Other non-cash operating activities	8	10	12
Postretirement benefits contributions	(243)	(29)	(222)
Proceeds from government grant			69
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	104	(16)	(116)
Decrease (increase) in inventories	144	(36)	205
Increase (decrease) in accounts payable and accrued refunds	(22)	47	12
Other current and non-current assets and liabilities	121	(242)	(134)
Net cash provided by operating activities	1,794	1,338	1,351
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,537)	(1,573)	(1,320)
Jackson plant acquisition	(154)
Cost to retire property	(89)	(75)	(56)
Other investing activities	(1)	(5)	(11)
Net cash used in investing activities	(1,781)	(1,653)	(1,387)
Cash Flows from Financing Activities
Proceeds from issuance of debt	250	878	750
Retirement of long-term debt	(124)	(220)	(466)
Payment of dividends on common and preferred stock	(476)	(459)	(408)
Stockholder contribution	150	495	150
Return of stockholder contribution		(178)
Increase (decrease) in notes payable	189	(110)	60
Payment of capital lease obligations and other financing costs	(23)	(38)	(37)
Net cash provided by financing activities	(34)	368	49
Net Increase in Cash and Cash Equivalents	(21)	53	13
Cash and Cash Equivalents, Beginning of Period	71	18	5
Cash and Cash Equivalents, End of Period	50	71	18
Cash transactions
Interest paid (net of amounts capitalized)	245	233	236
Income taxes paid (refunds received), net	(84)	266	225
Non-Cash Transactions
Capital expenditures not paid	182	201	176
Other assets placed under capital lease	$ 17	$ 7	$ 6