Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2011

Consumers Energy Company [Member] | Pension Plans, Defined Benefit [Member]

Schedule of Net Benefit Costs

In Millions
	Pension
	Three Months Ended						Six Months Ended
June 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic pension cost
Service cost	$	12		$	11		$	24		$	22
Interest expense		25			25			50			49
Expected return on plan assets		(28	)		(23	)		(56	)		(46	)
Amortization of:
Net loss		15			13			31			26
Prior service cost		2			1			3			3
Net periodic pension cost	$	26		$	27		$	52		$	54
Regulatory adjustment1		—			21			—			23
Net periodic pension cost after regulatory adjustment	$	26		$	48		$	52		$	77

In Millions
	Pension
	Three Months Ended						Six Months Ended
June 30	2011			2010			2011			2010
Consumers
Net periodic pension cost
Service cost	$	11		$	10		$	23		$	21
Interest expense		25			24			49			48
Expected return on plan assets		(28	)		(22	)		(55	)		(45	)
Amortization of:
Net loss		16			13			31			25
Prior service cost		2			1			3			3
Net periodic pension cost	$	26		$	26		$	51		$	52
Regulatory adjustment1		—			21			—			23
Net periodic pension cost after regulatory adjustment	$	26		$	47		$	51		$	75

¹ Regulatory adjustments are the differences between amounts included in rates and the periodic benefit cost calculated. These regulatory adjustments were offset by surcharge revenues, resulting in no impact to net income for the periods presented.

Pension Plans, Defined Benefit [Member]

Schedule of Net Benefit Costs

In Millions
	Pension
	Three Months Ended						Six Months Ended
June 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic pension cost
Service cost	$	12		$	11		$	24		$	22
Interest expense		25			25			50			49
Expected return on plan assets		(28	)		(23	)		(56	)		(46	)
Amortization of:
Net loss		15			13			31			26
Prior service cost		2			1			3			3
Net periodic pension cost	$	26		$	27		$	52		$	54
Regulatory adjustment1		—			21			—			23
Net periodic pension cost after regulatory adjustment	$	26		$	48		$	52		$	77

In Millions
	Pension
	Three Months Ended						Six Months Ended
June 30	2011			2010			2011			2010
Consumers
Net periodic pension cost
Service cost	$	11		$	10		$	23		$	21
Interest expense		25			24			49			48
Expected return on plan assets		(28	)		(22	)		(55	)		(45	)
Amortization of:
Net loss		16			13			31			25
Prior service cost		2			1			3			3
Net periodic pension cost	$	26		$	26		$	51		$	52
Regulatory adjustment1		—			21			—			23
Net periodic pension cost after regulatory adjustment	$	26		$	47		$	51		$	75

¹ Regulatory adjustments are the differences between amounts included in rates and the periodic benefit cost calculated. These regulatory adjustments were offset by surcharge revenues, resulting in no impact to net income for the periods presented.

Consumers Energy Company [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]

Schedule of Net Benefit Costs

In Millions
	OPEB
	Three Months Ended						Six Months Ended
June 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic OPEB cost
Service cost	$	6		$	6		$	13		$	13
Interest expense		19			20			38			41
Expected return on plan assets		(16	)		(14	)		(33	)		(29	)
Amortization of:
Net loss		8			8			16			16
Prior service cost		(5	)		(5	)		(10	)		(7	)
Net periodic OBEB cost	$	12		$	15		$	24		$	34
Regulatory adjustment1		—			6			—			7
Net periodic OPEB cost after regulatory adjustment	$	12		$	21		$	24		$	41
Consumers
Net periodic OPEB cost
Service cost	$	7		$	6		$	13		$	13
Interest expense		19			20			37			40
Expected return on plan assets		(16	)		(14	)		(31	)		(28	)
Amortization of:
Net loss		8			8			16			16
Prior service cost		(5	)		(4	)		(10	)		(6	)
Net periodic OPEB cost	$	13		$	16		$	25		$	35
Regulatory adjustment1		—			6			—			7
Net periodic OPEB cost after regulatory adjustment	$	13		$	22		$	25		$	42

¹ Regulatory adjustments are the differences between amounts included in rates and the periodic benefit cost calculated. These regulatory adjustments were offset by surcharge revenues, resulting in no impact to net income for the periods presented.

Other Postretirement Benefit Plans, Defined Benefit [Member]

Schedule of Net Benefit Costs

In Millions
	OPEB
	Three Months Ended						Six Months Ended
June 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic OPEB cost
Service cost	$	6		$	6		$	13		$	13
Interest expense		19			20			38			41
Expected return on plan assets		(16	)		(14	)		(33	)		(29	)
Amortization of:
Net loss		8			8			16			16
Prior service cost		(5	)		(5	)		(10	)		(7	)
Net periodic OBEB cost	$	12		$	15		$	24		$	34
Regulatory adjustment1		—			6			—			7
Net periodic OPEB cost after regulatory adjustment	$	12		$	21		$	24		$	41
Consumers
Net periodic OPEB cost
Service cost	$	7		$	6		$	13		$	13
Interest expense		19			20			37			40
Expected return on plan assets		(16	)		(14	)		(31	)		(28	)
Amortization of:
Net loss		8			8			16			16
Prior service cost		(5	)		(4	)		(10	)		(6	)
Net periodic OPEB cost	$	13		$	16		$	25		$	35
Regulatory adjustment1		—			6			—			7
Net periodic OPEB cost after regulatory adjustment	$	13		$	22		$	25		$	42

¹ Regulatory adjustments are the differences between amounts included in rates and the periodic benefit cost calculated. These regulatory adjustments were offset by surcharge revenues, resulting in no impact to net income for the periods presented.