Retirement Benefits (Tables)

9 Months Ended

Sep. 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 nine months ended September 30, 2013, and 2012:

	Pension Benefits (a)												Postretirement Benefits (a)
	Three Months						Nine Months						Three Months						Nine Months
	2013			2012			2013			2012			2013			2012			2013			2012
Service cost	$	23		$	20		$	69		$	61		$	6		$	5		$	17		$	16
Interest cost	40			42			121			125			11			12			34			36
Expected return on plan assets	(54		)	(52		)	(162		)	(156		)	(16		)	(14		)	(47		)	(42		)
Amortization of:
Transition obligation	—			—			—			—			—			1			—			1
Prior service cost (benefit)	(1		)	(1		)	(3		)	(3		)	(1		)	(1		)	(3		)	(3		)
Actuarial loss	23			19			69			56			2			1			6			3
Net periodic benefit cost	$	31		$	28		$	94		$	83		$	2		$	4		$	7		$	11

(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 respective shares of Ameren’s pension and postretirement costs. The following table presents the pension costs and the postretirement benefit costs incurred for the three and nine months ended September 30, 2013, and 2012:

	Pension Costs								Postretirement Costs
	Three Months				Nine Months				Three Months				Nine Months
	2013		2012		2013		2012		2013		2012		2013		2012
Ameren Missouri	$	18	$	16	$	54	$	48	$	2	$	2	$	7	$	7
Ameren Illinois	10		9		31		27		(b)		1		(b)		3
Other	3		3		9		8		(b)		1		(b)		1
Ameren(a)	$	31	$	28	$	94	$	83	$	2	$	4	$	7	$	11

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

(b) Less than $1 million.