Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2014

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 months ended March 31, 2014, and 2013:

	Pension Benefits						Postretirement Benefits
	Three Months						Three Months
	2014			2013			2014			2013
Service cost	$	21		$	24		$	5		$	6
Interest cost	49			40			13			12
Expected return on plan assets	(57		)	(54		)	(16		)	(16		)
Amortization of:
Prior service cost (benefit)	—			(1		)	(1		)	(1		)
Actuarial loss	12			22			(1		)	2
Net periodic benefit cost	$	25		$	31		$	—		$	3

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 months ended March 31, 2014, and 2013:

	Pension Costs				Postretirement Costs
	Three Months					Three Months
	2014		2013			2014			2013
Ameren Missouri	$	17	$	18		$	1		$	2
Ameren Illinois	8		10			(1		)	1
Other	—		3			—			—
Ameren(a)	$	25	$	31		$	—		$	3

(a) Includes amounts for Ameren registrants and nonregistrant subsidiaries.