Retirement Benefits (Tables)

12 Months Ended

Dec. 31, 2015

Summary Of Benefit Liability Recorded

The following table presents the net benefit liability recorded on the balance sheets of each of the Ameren Companies as of December 31, 2015 and 2014:

	2015		2014
Ameren(a)	$	567	$	710
Ameren Missouri	236		277
Ameren Illinois	219		278

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

Funded Status Of Benefit Plans And Amounts Included In Regulatory Assets And OCI

The following table presents the funded status of Ameren's pension and postretirement benefit plans as of December 31, 2015 and 2014. It also provides the amounts included in regulatory assets and accumulated OCI at December 31, 2015 and 2014, that have not been recognized in net periodic benefit costs.

	2015						2014
	Pension Benefits(a)				Postretirement Benefits(a)		Pension Benefits(a)				Postretirement Benefits(a)
Accumulated benefit obligation at end of year	$	3,995		$	(b)		$	4,176		$	(b)
Change in benefit obligation:
Net benefit obligation at beginning of year	$	4,410		$	1,203		$	3,900		$	1,096
Service cost	92				24		79				19
Interest cost	174				48		183				50
Participant contributions	—				8		—				16
Actuarial (gain) loss	(256		)		(133	)	462				84
Settlement	(2		)		—		—				—
Benefits paid	(221		)		(56	)	(214		)		(65	)
Federal subsidy on benefits paid	(b)				—		(b)				3
Net benefit obligation at end of year	4,197				1,094		4,410				1,203
Change in plan assets:
Fair value of plan assets at beginning of year	3,794				1,109		3,461				1,074
Actual return on plan assets	(29		)		(8	)	448				75
Employer contributions	111				18		99				6
Federal subsidy on benefits paid	(b)				—		(b)				3
Participant contributions	—				8		—				16
Settlements	(2		)		—		—				—
Benefits paid	(221		)		(56	)	(214		)		(65	)
Fair value of plan assets at end of year	3,653				1,071		3,794				1,109
Funded status – deficiency	544				23		616				94
Accrued benefit cost at December 31	$	544		$	23		$	616		$	94
Amounts recognized in the balance sheet consist of:
Noncurrent asset(c)	$	—		$	(18	)	$	—		$	—
Current liability(d)	3				2		3				2
Noncurrent liability	541				39		613				92
Net liability recognized	$	544		$	23		$	616		$	94
Amounts recognized in regulatory assets consist of:
Net actuarial (gain) loss	$	395		$	(82	)	$	452		$	(7	)
Prior service cost (credit)	(5		)		(11	)	(6		)		(16	)
Amounts (pretax) recognized in accumulated OCI consist of:
Net actuarial (gain) loss	17				(3	)	29				(5	)
Prior service cost (credit)	—				—		—				(1	)
Total	$	407		$	(96	)	$	475		$	(29	)

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

(b) Not applicable.

(c) Included in "Other assets" on Ameren's consolidated balance sheet.

(d) Included in "Other current liabilities" on Ameren's consolidated balance sheet.

Assumptions Used To Determine Benefit Obligations

The following table presents the assumptions used to determine our benefit obligations at December 31, 2015 and 2014:

	Pension Benefits				Postretirement Benefits
	2015		2014		2015		2014
Discount rate at measurement date	4.50	%	4.00	%	4.50	%	4.00	%
Increase in future compensation	3.50		3.50		3.50		3.50
Medical cost trend rate (initial)	(a)		(a)		5.00		5.00
Medical cost trend rate (ultimate)	(a)		(a)		5.00		5.00
Years to ultimate rate	(a)		(a)		—		—

(a) Not applicable

Schedule Of Cash Contributions Made To Benefit Plans

The following table presents the cash contributions made to our defined benefit retirement plan and to our postretirement plans during 2015, 2014, and 2013:

	Pension Benefits						Postretirement Benefits
	2015		2014		2013		2015		2014		2013
Ameren Missouri	$	47	$	41	$	60	$	8	$	3	$	10
Ameren Illinois	45		39		50		8		2		11
Other	19		19		46		2		1		4
Ameren(a)	111		99		156		18		6		25

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

Target Allocation Of The Plans' Asset Categories

The following table presents our target allocations for 2016 and our pension and postretirement plans’ asset categories as of December 31, 2015 and 2014:

Asset Category	Target Allocation 2016	Percentage of Plan Assets at December  31,
		2015		2014
Pension Plan:
Cash and cash equivalents	0% – 5%	1	%	2	%
Equity securities:
U.S. large-capitalization	29% – 39%	34	%	34	%
U.S. small- and mid-capitalization	3% – 13%	7	%	7	%
International and emerging markets	9% – 19%	13	%	12	%
Total equity	51% – 61%	54	%	53	%
Debt securities	35% – 45%	40	%	41	%
Real estate	0% –  9%	5	%	4	%
Private equity	0% –  5%	(a)		(a)
Total		100	%	100	%
Postretirement Plans:
Cash and cash equivalents	0% – 7%	4	%	4	%
Equity securities:
U.S. large-capitalization	34% – 44%	39	%	40	%
U.S. small- and mid-capitalization	2% – 12%	7	%	7	%
International	9% – 19%	13	%	13	%
Total equity	55% – 65%	59	%	60	%
Debt securities	33% – 43%	37	%	36	%
Total		100	%	100	%

(a) Less than 1% of plan assets.

Changes In The Fair Value Of Plan Assets Classified As Level 3

The following table summarizes the changes in the fair value of the pension plan assets classified as Level 3 in the fair value hierarchy for each of the years ended December 31, 2015 and 2014:

	Beginning Balance at January 1,		Actual Return on Plan Assets Related to Assets Still Held at the Reporting Date			Actual Return on Plan Assets Related to Assets Sold During the Period		Purchases, Sales, and Settlements, Net			Net Transfers into (out of) of Level 3		Ending Balance at December 31,
2015:
Real estate	$	147	$	14		$	—	$	7		$	—	$	168
Private equity	13		(9		)	9		(5		)	—		8
2014:
Real estate	$	131	$	11		$	—	$	5		$	—	$	147
Private equity	15		(9		)	10		(3		)	—		13

Components Of Net Periodic Benefit Cost

The following table presents the components of the net periodic benefit cost of Ameren's pension and postretirement benefit plans during 2015, 2014, and 2013:

	Pension Benefits(a)			Postretirement Benefits(a)
2015
Service cost	$	92		$	24
Interest cost	174			48
Expected return on plan assets	(248		)	(68		)
Amortization of:
Prior service credit	(1		)	(5		)
Actuarial loss	74			5
Settlement Loss	1			—
Net periodic benefit cost	$	92		$	4
2014
Service cost	$	79		$	19
Interest cost	183			50
Expected return on plan assets	(229		)	(65		)
Amortization of:
Prior service credit	(1		)	(5		)
Actuarial (gain) loss	49			(7		)
Net periodic benefit cost (benefit)	$	81		$	(8	)
2013
Service cost	$	91		$	22
Interest cost	163			46
Expected return on plan assets	(218		)	(62		)
Amortization of:
Prior service credit	(2		)	(6		)
Actuarial loss	87			8
Curtailment gain	(12		)	(7		)
Net periodic benefit cost(b)	$	109		$	1

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

(b) The net periodic benefit cost includes a $6 million and a $7 million net gain for pension benefits and postretirement benefits, respectively, which was included in "Income (loss) from discontinued operations, net of taxes" on Ameren's consolidated statement of income (loss). This net gain includes the curtailment gain recognized in 2013 as a result of a significant reduction in employees as of the December 2, 2013 closing date of the New AER divestiture. See Note 16 – Divestiture Transactions and Discontinued Operations for additional information on the divestiture.

Summary Of Estimated Amortizable Amounts From Regulatory Assets and Accumulated OCI Into Net Periodic Benefit Cost

The estimated amounts that will be amortized from regulatory assets and accumulated OCI into Ameren's net periodic benefit cost in 2016 are as follows:

	Pension Benefits(a)			Postretirement Benefits(a)
Regulatory assets:
Prior service credit	$	(1	)	$	(4	)
Net actuarial loss	46			(3		)
Accumulated OCI:
Net actuarial (gain) loss	(3		)	(2		)
Total	$	42		$	(9	)

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

Summary Of Benefit Plan Costs Incurred

The Ameren Companies are responsible for their share of the pension and postretirement benefit costs. The following table presents the pension costs and the postretirement benefit costs incurred and included in continuing operations for the years ended December 31, 2015, 2014, and 2013:

	Pension Costs						Postretirement Costs
	2015		2014		2013		2015			2014			2013
Ameren Missouri(a)	$	54	$	50	$	69	$	8		$	3		$	8
Ameren Illinois	38		30		41		(3		)	(9		)	—
Other	—		1		5		(1		)	(2		)	—
Ameren(b)	92		81		115		4			(8		)	8

(a) Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

(b) Includes amounts for Ameren registrant and nonregistrant subsidiaries.

Schedule Of Expected Payments From Qualified Trust And Company Funds

The expected pension and postretirement benefit payments from qualified trust and company funds, which reflect expected future service, as of December 31, 2015, are as follows:

	Pension Benefits				Postretirement Benefits
	Paid from Qualified Trust Funds		Paid from          Company       Funds		Paid from          Qualified       Trust Funds		Paid from          Company       Funds
2016	$	233	$	3	$	55	$	2
2017	244		3		58		2
2018	250		3		60		2
2019	257		3		62		2
2020	261		3		65		2
2021 – 2025	1,377		13		341		12

Assumptions Used To Determine Net Periodic Benefit Cost

The following table presents the assumptions used to determine net periodic benefit cost for our pension and postretirement benefit plans for the years ended December 31, 2015, 2014, and 2013:

	Pension Benefits						Postretirement Benefits
	2015		2014		2013		2015		2014		2013
Discount rate at measurement date	4.00	%	4.75	%	4.00	%	4.00	%	4.75	%	4.00	%
Expected return on plan assets	7.25		7.25		7.50		7.00		7.00		7.25
Increase in future compensation	3.50		3.50		3.50		3.50		3.50		3.50
Medical cost trend rate (initial)	(a)		(a)		(a)		5.00		5.00		5.00
Medical cost trend rate (ultimate)	(a)		(a)		(a)		5.00		5.00		5.00
Years to ultimate rate	(a)		(a)		(a)		—		—		—

(a) Not applicable

Schedule Of Potential Changes In Key Assumptions

The table below reflects the sensitivity of Ameren’s plans to potential changes in key assumptions:

	Pension Benefits					Postretirement Benefits
	Service Cost and Interest Cost			Projected     Benefit      Obligation		Service Cost     and Interest     Cost			Postretirement       Benefit        Obligation
0.25% decrease in discount rate	$	(1	)	$	130	$	1		$	37
0.25% increase in salary scale	2			14		—			—
1.00% increase in annual medical trend	—			—		3			44
1.00% decrease in annual medical trend	—			—		(3		)	(44		)

Schedule Of Matching Contributions

The following table presents the portion of the matching contribution to the Ameren 401(k) plan attributable to the continuing operations for each of the Ameren Companies for the years ended December 31, 2015, 2014, and 2013:

	2015		2014		2013
Ameren Missouri	$	16	$	16	$	16
Ameren Illinois	12		11		10
Other	1		1		1
Ameren(a)	29		28		27

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

Pension Benefits

Target Allocation Of The Plans' Asset Categories

The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plan assets measured at fair value as of December 31, 2015:

	Quoted Prices in Active Markets for Identified Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Cash and cash equivalents	$	—	$	20	$	—	$	20
Equity securities:
U.S. large-capitalization	—		1,296		—		1,296
U.S. small- and mid-capitalization	268		—		—		268
International and emerging markets	122		369		—		491
Debt securities:
Corporate bonds	—		631		—		631
Municipal bonds	—		104		—		104
U.S. Treasury and agency securities	6		751		—		757
Other	—		5		—		5
Real estate	—		—		168		168
Private equity	—		—		8		8
Total	$	396	$	3,176	$	176	$	3,748
Less: Medical benefit assets at December 31(a)							(123		)
Plus: Net receivables at December 31(b)							28
Fair value of pension plans assets at year end							$	3,653

(a) Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.

(b) Receivables related to pending security sales, offset by payables related to pending security purchases.

The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plan assets measured at fair value as of December 31, 2014:

	Quoted Prices in Active Markets for Identified Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Cash and cash equivalents	$	—	$	38	$	—	$	38
Equity securities:
U.S. large-capitalization	—		1,331		—		1,331
U.S. small- and mid-capitalization	270		—		—		270
International and emerging markets	134		360		—		494
Debt securities:
Corporate bonds	—		1,026		—		1,026
Municipal bonds	—		175		—		175
U.S. Treasury and agency securities	6		366		—		372
Other	—		31		—		31
Real estate	—		—		147		147
Private equity	—		—		13		13
Derivative assets	1		—		—		1
Total	$	411	$	3,327	$	160	$	3,898
Less: Medical benefit assets at December 31(a)							(125		)
Plus: Net receivables at December 31(b)							21
Fair value of pension plans assets at year end							$	3,794

(a) Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.

(b) Receivables related to pending security sales, offset by payables related to pending security purchases.

Postretirement Benefits

Target Allocation Of The Plans' Asset Categories

The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2015:

	Quoted Prices in Active Markets for Identified Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Cash and cash equivalents	$	61	$	—	$	—	$	61
Equity securities:
U.S. large-capitalization	272		98		—		370
U.S. small- and mid-capitalization	65		—		—		65
International	33		93		—		126
Other	—		7		—		7
Debt securities:
Corporate bonds	—		138		—		138
Municipal bonds	—		114		—		114
U.S. Treasury and agency securities	—		55		—		55
Other	—		40		—		40
Total	$	431	$	545	$	—	$	976
Plus: Medical benefit assets at December 31(a)							123
Less: Net payables at December 31(b)							(28		)
Fair value of postretirement benefit plans assets at year end							$	1,071

(a) Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.

(b) Payables related to pending security purchases, offset by interest receivables and receivables related to pending security sales.

The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans assets measured at fair value as of December 31, 2014:

	Quoted Prices in Active Markets for Identified Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Cash and cash equivalents	$	89	$	—	$	—	$	89
Equity securities:
U.S. large-capitalization	291		101		—		392
U.S. small- and mid-capitalization	70		—		—		70
International	37		94		—		131
Other	—		7		—		7
Debt securities:
Corporate bonds	—		105		—		105
Municipal bonds	—		111		—		111
U.S. Treasury and agency securities	—		89		—		89
Other	—		44		—		44
Total	$	487	$	551	$	—	$	1,038
Plus: Medical benefit assets at December 31(a)							125
Less: Net payables at December 31(b)							(54		)
Fair value of postretirement benefit plans assets at year end							$	1,109

(a) Medical benefit (health and welfare) component for 401(h) accounts to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.

(b) Payables related to pending security purchases, offset by Medicare, interest receivables, and receivables related to pending security sales.