Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash Flows from Operating Activities
Net income	$ 67	$ 135
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	172	162
Deferred income taxes and investment tax credit	42	73
Postretirement benefits expense	47	40
Other non-cash operating activities	19	21
Postretirement benefits contributions	(19)	(19)
Changes in other assets and liabilities:
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	99	9
Decrease (increase) in accrued power supply revenue	0	15
Decrease (increase) in inventories	312	462
Increase (decrease) in accounts payable	(89)	(9)
Increase (decrease) in accrued expenses	(109)	(89)
Decrease (increase) in other current and non-current assets	113	29
Increase (decrease) in other current and non-current liabilities	(19)	12
Net cash provided by operating activities	635	841
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(294)	(191)
Cost to retire property	(7)	(17)
Other investing activities	(12)	(20)
Net cash used in investing activities	(313)	(228)
Cash Flows from Financing Activities
Proceeds from issuance of long-term debt	390	0
Proceeds from EnerBank notes, net	15	13
Retirement of long-term debt	(459)	(13)
Payment of common stock dividends	(62)	(53)
Payment of capital and finance lease obligations	(6)	(6)
Other financing costs	(3)	(2)
Net cash (used in) provided by financing activities	(125)	(61)
Net (Decrease) Increase in Cash and Cash Equivalents, Including Assets Held for Sale	197	552
Decrease (Increase) in Cash and Cash Equivalents Included in Assets Held for Sale	0	2
Net (Decrease) Increase in Cash and Cash Equivalents	197	554
Cash and Cash Equivalents, Beginning of Period	161	247
Cash and Cash Equivalents, End of Period	358	801
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	76	153
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	171	161
Deferred income taxes and investment tax credit	20	39
Postretirement benefits expense	46	39
Other non-cash operating activities	19	17
Postretirement benefits contributions	(18)	(19)
Changes in other assets and liabilities:
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	100	6
Decrease (increase) in accrued power supply revenue	0	15
Decrease (increase) in inventories	302	458
Increase (decrease) in accounts payable	(74)	3
Increase (decrease) in accrued expenses	(69)	(49)
Decrease (increase) in other current and non-current assets	112	30
Increase (decrease) in other current and non-current liabilities	(4)	14
Net cash provided by operating activities	681	867
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(294)	(186)
Cost to retire property	(7)	(17)
Other investing activities	(11)	(25)
Net cash used in investing activities	(312)	(228)
Cash Flows from Financing Activities
Retirement of long-term debt	(310)	(9)
Payment of common stock dividends	(115)	(104)
Stockholders contribution	150	125
Payment of capital and finance lease obligations	(6)	(6)
Other financing costs	0	(3)
Net cash (used in) provided by financing activities	(281)	3
Net (Decrease) Increase in Cash and Cash Equivalents	88	642
Cash and Cash Equivalents, Beginning of Period	85	71
Cash and Cash Equivalents, End of Period	$ 173	$ 713