Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash Flows from Operating Activities
Net income	$ 417	$ 343	$ 240
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	546	576	570
Deferred income taxes and investment tax credit	167	227	122
Postretirement benefits expense	161	213	181
Bad debt expense	74	57	54
Other non-cash operating activities	33	39	(50)
Postretirement benefits contributions	(323)	(463)	(262)
Changes in other assets and liabilities:
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	104	(105)	(91)
Decrease (increase) in accrued power supply revenue	15	33	(41)
Decrease (increase) in inventories	(14)	133	86
Increase (decrease) in accounts payable	30	(7)	(50)
Increase (decrease) in accrued expenses	(34)	22	(6)
Decrease (increase) in other current and non-current assets	(48)	(28)	59
Increase (decrease) in current and non-current regulatory liabilities	49	(69)	102
Increase (decrease) in other current and non-current liabilities	(8)	(12)	(66)
Net cash provided by operating activities	1,169	959	848
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(882)	(821)	(818)
Cost to retire property	(54)	(43)	(49)
Cash effect of deconsolidation of partnerships	0	(10)	0
Increase in EnerBank loans receivable	(100)	(131)	(83)
Other investing activities	(22)	2	15
Net cash used in investing activities	(1,058)	(1,003)	(935)
Cash Flows from Financing Activities
Proceeds from issuance of long-term debt	375	1,400	1,218
Proceeds from EnerBank notes, net	98	149	39
Issuance of common stock	29	10	9
Retirement of long-term debt	(413)	(878)	(1,154)
Payment of DOE liability	(43)	0	0
Payment of common stock dividends	(211)	(154)	(114)
Payment of preferred stock dividends	0	(8)	(11)
Redemption of preferred stock	0	(239)	(4)
Payment of capital and finance lease obligations	(24)	(23)	(23)
Increase (decrease) in notes payable	0	(40)	40
Other financing costs	(10)	(15)	(35)
Net cash (used in) provided by financing activities	(199)	202	(35)
Net (Decrease) Increase in Cash and Cash Equivalents, Including Assets Held for Sale	(88)	158	(122)
Decrease (Increase) in Cash and Cash Equivalents Included in Assets Held for Sale	2	(1)	5
Net (Decrease) Increase in Cash and Cash Equivalents	(86)	157	(117)
Cash and Cash Equivalents, Beginning of Period	247	90	207
Cash and Cash Equivalents, End of Period	161	247	90
Cash transactions
Interest paid (net of amounts capitalized)	397	405	422
Income taxes paid	27	14	17
Non Cash Transactions Abstract
Capital expenditures not paid	92	56	15
Other assets placed under capital lease	4	16	16
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	467	434	293
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	542	572	559
Deferred income taxes and investment tax credit	161	246	67
Postretirement benefits expense	158	208	177
Bad debt expense	70	53	47
Other non-cash operating activities	16	24	(9)
Postretirement benefits contributions	(315)	(447)	(254)
Changes in other assets and liabilities:
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	97	(92)	(92)
Decrease (increase) in accrued power supply revenue	15	33	(41)
Decrease (increase) in inventories	(17)	132	91
Increase (decrease) in accounts payable	43	(16)	(50)
Increase (decrease) in accrued expenses	74	(83)	2
Decrease (increase) in other current and non-current assets	(49)	(21)	60
Increase (decrease) in current and non-current regulatory liabilities	49	(69)	101
Increase (decrease) in other current and non-current liabilities	12	(64)	(29)
Net cash provided by operating activities	1,323	910	922
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(876)	(815)	(811)
Cost to retire property	(56)	(43)	(49)
Other investing activities	(19)	(1)	10
Net cash used in investing activities	(951)	(859)	(850)
Cash Flows from Financing Activities
Proceeds from issuance of long-term debt	0	600	500
Retirement of long-term debt	(37)	(482)	(387)
Payment of DOE liability	(43)	0	0
Payment of common stock dividends	(374)	(358)	(285)
Payment of preferred stock dividends	(2)	(2)	(2)
Stockholder's contribution	125	250	100
Payment of capital and finance lease obligations	(24)	(23)	(23)
Other financing costs	(3)	(4)	(5)
Net cash (used in) provided by financing activities	(358)	(19)	(102)
Net (Decrease) Increase in Cash and Cash Equivalents	14	32	(30)
Cash and Cash Equivalents, Beginning of Period	71	39	69
Cash and Cash Equivalents, End of Period	85	71	39
Cash transactions
Interest paid (net of amounts capitalized)	253	259	276
Income taxes paid	8	149	104
Non Cash Transactions Abstract
Capital expenditures not paid	92	56	15
Other assets placed under capital lease	$ 4	$ 16	$ 16