Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2016

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Net Benefit Costs

In Millions
	DB Pension Plan												OPEB Plan
	Three Months Ended						Six Months Ended						Three Months Ended						Six Months Ended
June 30	2016			2015			2016			2015			2016			2015			2016			2015
CMS Energy, including Consumers
Net periodic cost (credit)
Service cost		$	10		$	12		$	21		$	24		$	4		$	6		$	9		$	12
Interest expense			22			26			43			51			11			14			23			29
Expected return on plan assets			(37)			(35)			(74)			(69)			(21)			(22)			(43)			(45)
Amortization of:
Net loss			18			22			35			45			6			6			11			11
Prior service cost (credit)			1			1			2			1			(11)			(11)			(21)			(21)
Net periodic cost (credit)		$	14		$	26		$	27		$	52		$	(11)		$	(7)		$	(21)		$	(14)
Consumers
Net periodic cost (credit)
Service cost		$	10		$	12		$	20		$	24		$	5		$	6		$	9		$	12
Interest expense			21			24			42			49			11			14			22			28
Expected return on plan assets			(36)			(34)			(72)			(67)			(20)			(21)			(40)			(43)
Amortization of:
Net loss			17			22			34			44			5			5			11			11
Prior service cost (credit)			1			1			2			1			(10)			(10)			(20)			(20)
Net periodic cost (credit)		$	13		$	25		$	26		$	51		$	(9)		$	(6)		$	(18)		$	(12)

Consumers Energy Company [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Net Benefit Costs

In Millions
	DB Pension Plan												OPEB Plan
	Three Months Ended						Six Months Ended						Three Months Ended						Six Months Ended
June 30	2016			2015			2016			2015			2016			2015			2016			2015
CMS Energy, including Consumers
Net periodic cost (credit)
Service cost		$	10		$	12		$	21		$	24		$	4		$	6		$	9		$	12
Interest expense			22			26			43			51			11			14			23			29
Expected return on plan assets			(37)			(35)			(74)			(69)			(21)			(22)			(43)			(45)
Amortization of:
Net loss			18			22			35			45			6			6			11			11
Prior service cost (credit)			1			1			2			1			(11)			(11)			(21)			(21)
Net periodic cost (credit)		$	14		$	26		$	27		$	52		$	(11)		$	(7)		$	(21)		$	(14)
Consumers
Net periodic cost (credit)
Service cost		$	10		$	12		$	20		$	24		$	5		$	6		$	9		$	12
Interest expense			21			24			42			49			11			14			22			28
Expected return on plan assets			(36)			(34)			(72)			(67)			(20)			(21)			(40)			(43)
Amortization of:
Net loss			17			22			34			44			5			5			11			11
Prior service cost (credit)			1			1			2			1			(10)			(10)			(20)			(20)
Net periodic cost (credit)		$	13		$	25		$	26		$	51		$	(9)		$	(6)		$	(18)		$	(12)