Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques

The following table describes the valuation techniques and unobservable inputs for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy as of March 31, 2015:

		Fair Value								Weighted Average
		Assets		Liabilities			Valuation Technique(s)	Unobservable Input	Range
Level 3 Derivative asset and liability - commodity contracts(a):
Ameren	Fuel oils	$	1	$	(7	)	Option model	Volatilities(%)(b)	33 - 80	42
							Discounted cash flow	Ameren Missouri credit risk(%)(b)(c)	0.40	(d)
	Natural gas	1		(1		)	Option model	Volatilities(%)(e)	6 - 39	33
								Nodal basis($/mmbtu)(e)	(0.40) - (0.20)	(0.30)
							Discounted cash flow	Nodal basis($/mmbtu)(e)	(0.40) - (0.10)	(0.30)
								Counterparty credit risk(%)(b)(c)	0.31 - 12.07	2.47
								Ameren Missouri and Ameren Illinois credit risk(%)(b)(c)	0.40	(d)
	Power(f)	5		(165		)	Discounted cash flow	Average forward peak and off-peak pricing - forwards/swaps($/MWh)(g)	22 - 46	32
								Estimated auction price for FTRs($/MW)(e)	(597) - 1,922	153
								Nodal basis($/MWh)(e)	(11) - 0	(3)
								Counterparty credit risk(%)(b)(c)	0.29 - 10.98	5.84
								Ameren Missouri and Ameren Illinois credit risk(%)(b)(c)	0.40	(d)
							Fundamental energy production model	Estimated future gas prices($/mmbtu)(e)	3 - 5	4
								Escalation rate(%)(e)(h)	1	(d)
							Contract price allocation	Estimated renewable energy credit costs($/credit)(e)	5 - 7	6
	Uranium	—		(1		)	Discounted cash flow	Average forward uranium pricing($/pound)(e)	40 - 43	40
Ameren Missouri	Fuel oils	$	1	$	(7	)	Option model	Volatilities(%)(b)	33 - 80	42
							Discounted cash flow	Ameren Missouri credit risk(%)(b)(c)	0.40	(d)
	Natural gas	—		(1		)	Option model	Volatilities(%)(e)	6 - 39	33
								Nodal basis($/mmbtu)(e)	(0.40) - (0.20)	(0.30)
							Discounted cash flow	Nodal basis($/mmbtu)(e)	(0.10)	(d)
								Counterparty credit risk(%)(b)(c)	0.54 - 12.07	5
								Ameren Missouri credit risk(%)(b)(c)	0.40	(d)
	Power(f)	5		(1		)	Discounted cash flow	Average forward peak and off-peak pricing - forwards/swaps($/MWh)(b)	24 - 46	36
								Estimated auction price for FTRs($/MW)(e)	(597) - 1,922	153
								Nodal basis($/MWh)(b)	(11) - (4)	(8)
								Counterparty credit risk(%)(b)(c)	0.29 - 10.98	5.84
	Uranium	—		(1		)	Discounted cash flow	Average forward uranium pricing($/pound)(e)	40 - 43	40
Ameren Illinois	Natural gas	$	1	$	—		Discounted cash flow	Nodal basis($/mmbtu)(e)	(0.40) - (0.10)	(0.30)
								Counterparty credit risk(%)(b)(c)	0.31 - 2.28	1.28
								Ameren Illinois credit risk(%)(b)(c)	0.40	(d)
	Power(f)	—		(164		)	Discounted cash flow	Average forward peak and off-peak pricing - forwards/swaps($/MWh)(e)	22 - 38	31
								Nodal basis($/MWh)(e)	(6) - 0	(3)
								Ameren Illinois credit risk(%)(b)(c)	0.40	(d)
							Fundamental energy production model	Estimated future gas prices($/mmbtu)(e)	3 - 5	4
								Escalation rate(%)(e)(h)	1	(d)
							Contract price allocation	Estimated renewable energy credit costs($/credit)(e)	5 - 7	6

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.

(c) Counterparty credit risk is applied only to counterparties with derivative asset balances. Ameren Missouri and Ameren Illinois credit risk is applied only to counterparties with derivative liability balances.

(d) Not applicable.

(e) Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.

(f) Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2018. Valuations beyond 2018 use fundamentally modeled pricing by month for peak and off-peak demand.

(g) The balance at Ameren is comprised of Ameren Missouri and Ameren Illinois power contracts, which respond differently to unobservable input changes due to their opposing positions. As such, refer to the power sensitivity analysis for each company above.

(h) Escalation rate applies to power prices 2026 and beyond.

The following table describes the valuation techniques and unobservable inputs for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy as of December 31, 2014:

		Fair Value								Weighted
		Assets		Liabilities			Valuation Technique(s)	Unobservable Input	Range	Average
Level 3 Derivative asset and liability – commodity contracts(a):
Ameren	Fuel oils	$	2	$	(8	)	Option model	Volatilities(%)(b)	3 - 39	32
							Discounted cash flow	Ameren Missouri credit risk(%)(b)(c)	0.43	(d)
								Escalation rate(%)(e)(f)	5	(d)
	Natural Gas	1		(2		)	Option model	Volatilities(%)(b)	31 - 144	63
								Nodal basis($/mmbtu)(e)	(0.40) - 0	(0.20)
							Discounted cash flow	Nodal basis($/mmbtu)(e)	(0.40) - 0.10	(0.20)
								Counterparty credit risk(%)(b)(c)	0.43 - 13	3
								Ameren Missouri and Ameren Illinois credit risk(%)(b)(c)	0.43	(d)
	Power(g)	11		(144		)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps($/MWh)(h)	27 - 50	32
								Estimated auction price for FTRs($/MW)(e)	(1,833) - 2,743	171
								Nodal basis($/MWh)(e)	(6) - 0	(2)
								Counterparty credit risk(%)(b)(c)	0.26	(d)
								Ameren Missouri and Ameren Illinois credit risk(%)(b)(c)	0.43	(d)
							Fundamental energy production model	Estimated future gas prices($/mmbtu)(e)	4 - 5	4
								Escalation rate(%)(e)(i)	0 - 1	1
							Contract price allocation	Estimated renewable energy credit costs($/credit)(e)	5 - 7	6
	Uranium	—		(2		)	Discounted cash flow	Average forward uranium pricing($/pound)(e)	35 - 40	36
Ameren Missouri	Fuel oils	$	2	$	(8	)	Option model	Volatilities(%)(b)	3 - 39	32
							Discounted cash flow	Ameren Missouri credit risk(%)(b)(c)	0.43	(d)
								Escalation rate(%)(e)(f)	5	(d)
	Natural Gas	—		(1		)	Option model	Volatilities(%)(b)	31 - 144	53
								Nodal basis($/mmbtu)(e)	(0.40) - 0	(0.30)
							Discounted cash flow	Nodal basis($/mmbtu)(e)	(0.10)	(d)
								Counterparty credit risk(%)(b)(c)	0.57 - 13	5
								Ameren Missouri credit risk(%)(b)(c)	0.43	(d)
	Power(g)	11		(2		)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps($/MWh)(b)	27 - 50	32
								Estimated auction price for FTRs($/MW)(e)	(1,833) - 2,743	171
								Counterparty credit risk(%)(b)(c)	0.26	(d)
								Ameren Missouri credit risk(%)(b)(c)	0.43	(d)
	Uranium	—		(2		)	Discounted cash flow	Average forward uranium pricing($/pound)(e)	35 - 40	36
Ameren Illinois	Natural Gas	$	1	$	(1	)	Option model	Volatilities(%)(b)	50 - 144	94
								Nodal basis($/mmbtu)(e)	(0.10) - 0	(0.10)
							Discounted cash flow	Nodal basis($/mmbtu)(e)	(0.40) - 0.10	(0.20)
								Counterparty credit risk(%)(b)(c)	0.43 - 2	0.83
								Ameren Illinois credit risk(%)(b)(c)	0.43	(d)
	Power(g)	—		(142		)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps($/MWh)(e)	27 - 38	32
								Nodal basis($/MWh)(e)	(6) - 0	(2)
								Ameren Illinois credit risk(%)(b)(c)	0.43	(d)
							Fundamental energy production model	Estimated future gas prices($/mmbtu)(e)	4 - 5	4
								Escalation rate(%)(e)(i)	0 - 1	1
							Contract price allocation	Estimated renewable energy credit costs($/credit)(e)	5 - 7	6

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.

(c) Counterparty credit risk is applied only to counterparties with derivative asset balances. Ameren Missouri and Ameren Illinois credit risk is applied only to counterparties with derivative liability balances.

(d) Not applicable.

(e) Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.

(f) Escalation rate applies to fuel oil prices 2017 and beyond.

(g) Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2018. Valuations beyond 2018 use fundamentally modeled pricing by month for peak and off-peak demand.

(h) The balance at Ameren is comprised of Ameren Missouri and Ameren Illinois power contracts, which respond differently to unobservable input changes due to their opposing positions. As such, refer to the power sensitivity analysis for each company above.

(i) Escalation rate applies to power prices 2026 and beyond.

Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of March 31, 2015:

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren	Derivative assets - commodity contracts(a):
	Fuel oils	$	—	$	—	$	1	$	1
	Natural gas	—		—		1		1
	Power	—		2		5		7
	Total derivative assets - commodity contracts	$	—	$	2	$	7	$	9
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	2	$	—	$	—	$	2
	Equity securities:
	U.S. large capitalization	368		—		—		368
	Debt securities:
	Corporate bonds	—		65		—		65
	U.S. treasury and agency securities	—		101		—		101
	Other	—		20		—		20
	Total nuclear decommissioning trust fund	$	370	$	186	$	—	$	556	(b)
	Total Ameren	$	370	$	188	$	7	$	565
Ameren	Derivative assets - commodity contracts(a):
Missouri	Fuel oils	$	—	$	—	$	1	$	1
	Power	—		2		5		7
	Total derivative assets - commodity contracts	$	—	$	2	$	6	$	8
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	2	$	—	$	—	$	2
	Equity securities:
	U.S. large capitalization	368		—		—		368
	Debt securities:
	Corporate bonds	—		65		—		65
	U.S. treasury and agency securities	—		101		—		101
	Other	—		20		—		20
	Total nuclear decommissioning trust fund	$	370	$	186	$	—	$	556	(b)
	Total Ameren Missouri	$	370	$	188	$	6	$	564
Ameren	Derivative assets - commodity contracts(a):
Illinois	Natural gas	$	—	$	—	$	1	$	1
Liabilities:
Ameren	Derivative liabilities - commodity contracts(a):
	Fuel oils	$	21	$	—	$	7	$	28
	Natural gas	—		63		1		64
	Power	—		—		165		165
	Uranium	—		—		1		1
	Total Ameren	$	21	$	63	$	174	$	258
Ameren	Derivative liabilities - commodity contracts(a):
Missouri	Fuel oils	$	21	$	—	$	7	$	28
	Natural gas	—		13		1		14
	Power	—		—		1		1
	Uranium	—		—		1		1
	Total Ameren Missouri	$	21	$	13	$	10	$	44
Ameren	Derivative liabilities - commodity contracts(a):
Illinois	Natural gas	$	—	$	50	$	—	$	50
	Power	—		—		164		164
	Total Ameren Illinois	$	—	$	50	$	164	$	214

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Balance excludes $2 million of receivables, payables, and accrued income, net.

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2014:

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren	Derivative assets - commodity contracts(a):
	Fuel oils	$	—	$	—	$	2	$	2
	Natural gas	—		1		1		2
	Power	—		4		11		15
	Total derivative assets - commodity contracts	$	—	$	5	$	14	$	19
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	1	$	—	$	—	$	1
	Equity securities:
	U.S. large capitalization	364		—		—		364
	Debt securities:
	Corporate bonds	—		63		—		63
	U.S. treasury and agency securities	—		102		—		102
	Other	—		17		—		17
	Total nuclear decommissioning trust fund	$	365	$	182	$	—	$	547	(b)
	Total Ameren	$	365	$	187	$	14	$	566
Ameren	Derivative assets - commodity contracts(a):
Missouri	Fuel oils	$	—	$	—	$	2	$	2
	Natural gas	—		1		—		1
	Power	—		4		11		15
	Total derivative assets - commodity contracts	$	—	$	5	$	13	$	18
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	1	$	—	$	—	$	1
	Equity securities:
	U.S. large capitalization	364		—		—		364
	Debt securities:
	Corporate bonds	—		63		—		63
	U.S. treasury and agency securities	—		102		—		102
	Other	—		17		—		17
	Total nuclear decommissioning trust fund	$	365	$	182	$	—	$	547	(b)
	Total Ameren Missouri	$	365	$	187	$	13	$	565
Ameren	Derivative assets - commodity contracts(a):
Illinois	Natural gas	$	—	$	—	$	1	$	1
Liabilities:
Ameren	Derivative liabilities - commodity contracts(a):
	Fuel oils	$	21	$	—	$	8	$	29
	Natural gas	1		53		2		56
	Power	—		1		144		145
	Uranium	—		—		2		2
	Total Ameren	$	22	$	54	$	156	$	232
Ameren	Derivative liabilities - commodity contracts(a):
Missouri	Fuel oils	$	21	$	—	$	8	$	29
	Natural gas	1		10		1		12
	Power	—		1		2		3
	Uranium	—		—		2		2
	Total Ameren Missouri	$	22	$	11	$	13	$	46
Ameren	Derivative liabilities - commodity contracts(a):
Illinois	Natural gas	$	—	$	43	$	1	$	44
	Power	—		—		142		142
	Total Ameren Illinois	$	—	$	43	$	143	$	186

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Balance excludes $2 million of receivables, payables, and accrued income, net.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended March 31, 2015:

		Net derivative commodity contracts
		Ameren Missouri			Ameren Illinois			Ameren
Fuel oils:
Beginning balance at January 1, 2015	$	(6	)	$	(a)		$	(6	)
Realized and unrealized gains (losses) included in regulatory assets/liabilities		(1	)		(a)			(1	)
Settlements		1			(a)			1
Ending balance at March 31, 2015	$	(6	)	$	(a)		$	(6	)
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2015	$	(3	)	$	(a)		$	(3	)
Natural gas:
Beginning balance at January 1, 2015	$	(1	)	$	—		$	(1	)
Purchases		—			1			1
Ending balance at March 31, 2015	$	(1	)	$	1		$	—
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2015	$	—		$	—		$	—
Power:
Beginning balance at January 1, 2015	$	9		$	(142	)	$	(133	)
Realized and unrealized gains (losses) included in regulatory assets/liabilities		(2	)		(25	)		(27	)
Settlements		(3	)		3			—
Ending balance at March 31, 2015	$	4		$	(164	)	$	(160	)
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2015	$	—		$	(24	)	$	(24	)
Uranium:
Beginning balance at January 1, 2015	$	(2	)	$	(a)		$	(2	)
Realized and unrealized gains (losses) included in regulatory assets/liabilities		1			(a)			1
Ending balance at March 31, 2015	$	(1	)	$	(a)		$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2015	$	1		$	(a)		$	1

(a) Not applicable.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended March 31, 2014:

		Net derivative commodity contracts
		Ameren Missouri			Ameren Illinois			Ameren
Fuel oils:
Beginning balance at January 1, 2014	$	5		$	(a)		$	5
Realized and unrealized gains (losses) included in regulatory assets/liabilities		(2	)		(a)			(2	)
Settlements		(2	)		(a)			(2	)
Ending balance at March 31, 2014	$	1		$	(a)		$	1
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2014	$	(1	)	$	(a)		$	(1	)
Natural gas:
Beginning balance at January 1, 2014	$	—		$	—		$	—
Purchases		—			(2	)		(2	)
Settlements		—			2			2
Ending balance at March 31, 2014	$	—		$	—		$	—
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2014	$	—		$	—		$	—
Power:
Beginning balance at January 1, 2014	$	19		$	(108	)	$	(89	)
Realized and unrealized gains (losses) included in regulatory assets/liabilities		(5	)		(12	)		(17	)
Settlements		(5	)		—			(5	)
Transfers out of Level 3		1			—			1
Ending balance at March 31, 2014	$	10		$	(120	)	$	(110	)
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2014	$	(1	)	$	(14	)	$	(15	)
Uranium:
Beginning balance at January 1, 2014	$	(6	)	$	(a)		$	(6	)
Settlements		1			(a)			1
Ending balance at March 31, 2014	$	(5	)	$	(a)		$	(5	)
Change in unrealized gains (losses) related to assets/liabilities held at March 31, 2014	$	—		$	(a)		$	—

(a) Not applicable.

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt, Capital Lease Obligations And Preferred Stock

The following table presents the carrying amounts and estimated fair values of our long-term debt, capital lease obligations and preferred stock at March 31, 2015, and December 31, 2014:

	March 31, 2015				December 31, 2014
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Ameren:(a)
Long-term debt and capital lease obligations (including current portion)	$	6,240	$	7,127	$	6,240	$	7,135
Preferred stock	142		123		142		122
Ameren Missouri:
Long-term debt and capital lease obligations (including current portion)	$	3,999	$	4,574	$	3,999	$	4,518
Preferred stock	80		74		80		73
Ameren Illinois:
Long-term debt	$	2,241	$	2,553	$	2,241	$	2,517
Preferred stock	62		49		62		49

(a) Preferred stock is recorded in “Noncontrolling Interests” on the consolidated balance sheet.