Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2013

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Components Of Net Periodic Benefit Cost

The following table presents the components of the net periodic benefit cost for Ameren’s pension and postretirement benefit plans for the three and six months ended June 30, 2013, and 2012:

	Pension Benefits (a)												Postretirement Benefits (a)
	Three Months						Six Months						Three Months						Six Months
	2013			2012			2013			2012			2013			2012			2013			2012
Service cost	$	22		$	20		$	46		$	41		$	5		$	5		$	11		$	11
Interest cost	41			41			81			83			11			11			23			24
Expected return on plan assets	(54		)	(52		)	(108		)	(104		)	(15		)	(14		)	(31		)	(28		)
Amortization of:
Prior service cost (benefit)	(1		)	(1		)	(2		)	(2		)	(1		)	(1		)	(2		)	(2		)
Actuarial loss	24			18			46			37			2			(1		)	4			2
Net periodic benefit cost	$	32		$	26		$	63		$	55		$	2		$	—		$	5		$	7

(a) Excludes the EEI plans as they are included in discontinued operations.

Summary Of Benefit Plan Costs Incurred

Ameren Missouri and Ameren Illinois are responsible for their share of the pension and postretirement costs. The following table presents the pension costs and the postretirement benefit costs incurred for the three and six months ended June 30, 2013, and 2012:

	Pension Costs								Postretirement Costs
	Three Months				Six Months				Three Months					Six Months
	2013		2012		2013		2012		2013			2012		2013		2012
Ameren Missouri	$	18	$	16	$	36	$	32	$	2		$	—	$	5	$	5
Ameren Illinois	11		8		21		18		(1		)	—		—		2
Other	3		2		6		5		1			—		—		—
Ameren(a)	$	32	$	26	$	63	$	55	$	2		$	—	$	5	$	7

(a) Includes amounts for Ameren registrants and nonregistrant subsidiaries, but excludes the EEI plans as they are included in discontinued operations.