Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2018

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Net Benefit Costs

In Millions
	DB Pension Plans						OPEB Plan
Three Months Ended March 31	2018			2017			2018			2017
CMS Energy, including Consumers
Net periodic cost (credit)
Service cost		$	12		$	11		$	4		$	5
Interest cost			22			22			9			13
Expected return on plan assets			(37)			(38)			(24)			(22)
Amortization of:
Net loss			18			20			4			8
Prior service cost (credit)			1			1			(17)			(9)
Net periodic cost (credit)		$	16		$	16		$	(24)		$	(5)
Consumers
Net periodic cost (credit)
Service cost		$	12		$	11		$	4		$	5
Interest cost			21			21			8			13
Expected return on plan assets			(35)			(37)			(23)			(21)
Amortization of:
Net loss			18			20			4			8
Prior service cost (credit)			1			1			(16)			(9)
Net periodic cost (credit)		$	17		$	16		$	(23)		$	(4)

Consumers Energy Company [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule Of Net Benefit Costs

In Millions
	DB Pension Plans						OPEB Plan
Three Months Ended March 31	2018			2017			2018			2017
CMS Energy, including Consumers
Net periodic cost (credit)
Service cost		$	12		$	11		$	4		$	5
Interest cost			22			22			9			13
Expected return on plan assets			(37)			(38)			(24)			(22)
Amortization of:
Net loss			18			20			4			8
Prior service cost (credit)			1			1			(17)			(9)
Net periodic cost (credit)		$	16		$	16		$	(24)		$	(5)
Consumers
Net periodic cost (credit)
Service cost		$	12		$	11		$	4		$	5
Interest cost			21			21			8			13
Expected return on plan assets			(35)			(37)			(23)			(21)
Amortization of:
Net loss			18			20			4			8
Prior service cost (credit)			1			1			(16)			(9)
Net periodic cost (credit)		$	17		$	16		$	(23)		$	(4)