Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2011

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

Schedule of Net Benefit Costs

In Millions
	Pension
	Three Months Ended						Nine Months Ended
September 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic pension cost
Service cost	$	12		$	11		$	36		$	33
Interest expense		25			25			75			74
Expected return on plan assets		(28	)		(24	)		(84	)		(70	)
Amortization of:
Net loss		16			13			47			39
Prior service cost		1			1			4			4
Net periodic pension cost	$	26		$	26		$	78		$	80
Regulatory adjustment1		—			7			—			30
Net periodic pension cost after regulatory adjustment	$	26		$	33		$	78		$	110
Consumers
Net periodic pension cost
Service cost	$	12		$	11		$	35		$	32
Interest expense		24			23			73			71
Expected return on plan assets		(27	)		(22	)		(82	)		(67	)
Amortization of:
Net loss		15			13			46			38
Prior service cost		1			1			4			4
Net periodic pension cost	$	25		$	26		$	76		$	78
Regulatory adjustment1		—			7			—			30
Net periodic pension cost after regulatory adjustment	$	25		$	33		$	76		$	108

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						Nine Months Ended
September 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic pension cost
Service cost	$	12		$	11		$	36		$	33
Interest expense		25			25			75			74
Expected return on plan assets		(28	)		(24	)		(84	)		(70	)
Amortization of:
Net loss		16			13			47			39
Prior service cost		1			1			4			4
Net periodic pension cost	$	26		$	26		$	78		$	80
Regulatory adjustment1		—			7			—			30
Net periodic pension cost after regulatory adjustment	$	26		$	33		$	78		$	110
Consumers
Net periodic pension cost
Service cost	$	12		$	11		$	35		$	32
Interest expense		24			23			73			71
Expected return on plan assets		(27	)		(22	)		(82	)		(67	)
Amortization of:
Net loss		15			13			46			38
Prior service cost		1			1			4			4
Net periodic pension cost	$	25		$	26		$	76		$	78
Regulatory adjustment1		—			7			—			30
Net periodic pension cost after regulatory adjustment	$	25		$	33		$	76		$	108

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						Nine Months Ended
September 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic OPEB cost
Service cost	$	7		$	7		$	20		$	20
Interest expense		20			20			58			61
Expected return on plan assets		(17	)		(16	)		(50	)		(45	)
Amortization of:
Net loss		7			8			23			24
Prior service cost		(5	)		(5	)		(15	)		(12	)
Net periodic OBEB cost	$	12		$	14		$	36		$	48
Regulatory adjustment1		—			(1	)		—			5
Net periodic OPEB cost after regulatory adjustment	$	12		$	13		$	36		$	53
Consumers
Net periodic OPEB cost
Service cost	$	7		$	6		$	20		$	19
Interest expense		19			19			56			59
Expected return on plan assets		(15	)		(14	)		(46	)		(42	)
Amortization of:
Net loss		7			8			23			24
Prior service cost		(5	)		(5	)		(15	)		(11	)
Net periodic OPEB cost	$	13		$	14		$	38		$	49
Regulatory adjustment1		—			(1	)		—			5
Net periodic OPEB cost after regulatory adjustment	$	13		$	13		$	38		$	54

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						Nine Months Ended
September 30	2011			2010			2011			2010
CMS Energy, including Consumers
Net periodic OPEB cost
Service cost	$	7		$	7		$	20		$	20
Interest expense		20			20			58			61
Expected return on plan assets		(17	)		(16	)		(50	)		(45	)
Amortization of:
Net loss		7			8			23			24
Prior service cost		(5	)		(5	)		(15	)		(12	)
Net periodic OBEB cost	$	12		$	14		$	36		$	48
Regulatory adjustment1		—			(1	)		—			5
Net periodic OPEB cost after regulatory adjustment	$	12		$	13		$	36		$	53
Consumers
Net periodic OPEB cost
Service cost	$	7		$	6		$	20		$	19
Interest expense		19			19			56			59
Expected return on plan assets		(15	)		(14	)		(46	)		(42	)
Amortization of:
Net loss		7			8			23			24
Prior service cost		(5	)		(5	)		(15	)		(11	)
Net periodic OPEB cost	$	13		$	14		$	38		$	49
Regulatory adjustment1		—			(1	)		—			5
Net periodic OPEB cost after regulatory adjustment	$	13		$	13		$	38		$	54

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.