Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2015

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	2015			2014			2015			2014			2015			2014			2015			2014
CMS Energy, including Consumers
Net periodic cost (credit)
Service cost		$	12		$	10		$	24		$	20		$	6		$	5		$	12		$	10
Interest expense			26			25			51			50			14			14			29			28
Expected return on plan assets			(35)			(34)			(69)			(68)			(22)			(22)			(45)			(44)
Amortization of:
Net loss			22			14			45			29			6			1			11			1
Prior service cost (credit)			1			1			1			1			(11)			(11)			(21)			(21)
Net periodic cost (credit)		$	26		$	16		$	52		$	32		$	(7)		$	(13)		$	(14)		$	(26)
Consumers
Net periodic cost (credit)
Service cost		$	12		$	10		$	24		$	20		$	6		$	5		$	12		$	10
Interest expense			24			24			49			48			14			14			28			27
Expected return on plan assets			(34)			(33)			(67)			(66)			(21)			(21)			(43)			(42)
Amortization of:
Net loss			22			14			44			28			5			1			11			2
Prior service cost (credit)			1			1			1			1			(10)			(10)			(20)			(20)
Net periodic cost (credit)		$	25		$	16		$	51		$	31		$	(6)		$	(11)		$	(12)		$	(23)

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	2015			2014			2015			2014			2015			2014			2015			2014
CMS Energy, including Consumers
Net periodic cost (credit)
Service cost		$	12		$	10		$	24		$	20		$	6		$	5		$	12		$	10
Interest expense			26			25			51			50			14			14			29			28
Expected return on plan assets			(35)			(34)			(69)			(68)			(22)			(22)			(45)			(44)
Amortization of:
Net loss			22			14			45			29			6			1			11			1
Prior service cost (credit)			1			1			1			1			(11)			(11)			(21)			(21)
Net periodic cost (credit)		$	26		$	16		$	52		$	32		$	(7)		$	(13)		$	(14)		$	(26)
Consumers
Net periodic cost (credit)
Service cost		$	12		$	10		$	24		$	20		$	6		$	5		$	12		$	10
Interest expense			24			24			49			48			14			14			28			27
Expected return on plan assets			(34)			(33)			(67)			(66)			(21)			(21)			(43)			(42)
Amortization of:
Net loss			22			14			44			28			5			1			11			2
Prior service cost (credit)			1			1			1			1			(10)			(10)			(20)			(20)
Net periodic cost (credit)		$	25		$	16		$	51		$	31		$	(6)		$	(11)		$	(12)		$	(23)