Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value Inputs, Assets and Liabilities, Quantitative Information

The following table describes the valuation techniques and unobservable inputs utilized by the Ameren Companies for the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the periods ended December 31, 2016 and 2015:

		Fair Value								Weighted
		Assets		Liabilities			Valuation Technique(s)	Unobservable Input	Range	Average
Level 3 Derivative asset and liability – commodity contracts(a):
2016
	Fuel oils	$	1	$	—		Option model	Volatilities(%)(b)	24 – 66	28
							Discounted cash flow	Counterparty credit risk(%)(c)(d)	0.13 – 0.22	0.15
								Ameren Missouri credit risk(%)(c)(d)	0.38	(e)
								Escalation rate(%)(b)(f)	(2) – 2	0
	Natural Gas	1		(1		)	Option model	Volatilities(%)(b)	31 – 66	36
								Nodal basis($/mmbtu)(b)	(0.40) – (0.10)	(0.20)
							Discounted cash flow	Nodal basis($/mmbtu)(b)	(0.80) – 0	(0.50)
								Counterparty credit risk(%)(c)(d)	0.13 – 8	1
								Ameren Illinois credit risk(%)(c)(d)	0.38	(e)
	Power(g)	9		(187		)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps($/MWh)(h)	26 – 44	29
								Estimated auction price for FTRs($/MW)(b)	(71) – 5,270	125
								Nodal basis($/MWh)(h)	(6) – 0	(2)
								Ameren Illinois credit risk(%)(c)(d)	0.38	(e)
							Fundamental energy production model	Estimated future natural gas prices($/mmbtu)(b)	3 – 4	3
								Escalation rate(%)(b)(i)	5	(e)
							Contract price allocation	Estimated renewable energy credit costs($/credit)(b)	5 – 7	6
	Uranium	—		(4		)	Option model	Volatilities(%)(b)	24	(e)
							Discounted cash flow	Average forward uranium pricing($/pound)(b)	22 – 24	22
								Ameren Missouri credit risk(%)(c)(d)	0.38	(e)
2015
	Natural Gas	$	1	$	(1	)	Option model	Volatilities(%)(b)	35 – 55	45
								Nodal basis($/mmbtu)(c)	(0.30) – 0	(0.20)
							Discounted cash flow	Nodal basis($/mmbtu)(b)	(0.10) – 0	(0.10)
								Counterparty credit risk(%)(c)(d)	0.40 – 12	7
								Ameren Missouri credit risk(%)(c)(d)	0.40	(e)
	Power(g)	16		(170		)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps($/MWh)(h)	22 – 39	29
								Estimated auction price for FTRs($/MW)(b)	(270) – 2,057	211
								Nodal basis($/MWh)(h)	(10) – (1)	(3)

	Fair Value						Weighted
	Assets	Liabilities		Valuation Technique(s)	Unobservable Input	Range	Average
					Counterparty credit risk(%)(c)(d)	0.86	(e)
					Ameren Illinois credit risk(%)(c)(d)	0.40	(e)
				Fundamental energy production model	Estimated future natural gas prices($/mmbtu)(b)	3 – 4	4
					Escalation rate(%)(b)(i)	3	(e)
				Contract price allocation	Estimated renewable energy credit costs($/credit)(b)	5 – 7	6
Uranium	—	(1	)	Option model	Volatilities(%)(b)	20	(e)
				Discounted cash flow	Average forward uranium pricing($/pound)(b)	35 – 42	37
					Ameren Missouri credit risk(%)(c)(d)	0.40	(e)

(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 higher (lower) fair value measurement.

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

(d) 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.

(e) Not applicable.

(f) Escalation rate applies to fuel oil prices 2019 and beyond.

(g) Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2020. Valuations beyond 2020 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 because of their opposing positions.

(i) Escalation rate applies to power prices in 2031 and beyond for December 31, 2016, and to power prices in 2026 and beyond for December 31, 2015.

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 December 31, 2016:

		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	$	—	$	1	$	3
	Natural gas	2		12		1		15
	Power	—		—		9		9
	Total derivative assets – commodity contracts	$	4	$	12	$	11	$	27
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	1	$	—	$	—	$	1
	Equity securities:
	U.S. large capitalization	408		—		—		408
	Debt securities:
	U.S. Treasury and agency securities	—		112		—		112
	Corporate bonds	—		67		—		67
	Other	—		17		—		17
	Total nuclear decommissioning trust fund	$	409	$	196	$	—	$	605	(b)
	Total Ameren	$	413	$	208	$	11	$	632
Ameren Missouri	Derivative assets – commodity contracts(a):

		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
	Fuel oils	$	2	$	—	$	1	$	3
	Natural gas	—		1		1		2
	Power	—		—		9		9
	Total derivative assets – commodity contracts	$	2	$	1	$	11	$	14
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	1	$	—	$	—	$	1
	Equity securities:
	U.S. large capitalization	408		—		—		408
	Debt securities:
	U.S. Treasury and agency securities	—		112		—		112
	Corporate bonds	—		67		—		67
	Other	—		17		—		17
	Total nuclear decommissioning trust fund	$	409	$	196	$	—	$	605	(b)
	Total Ameren Missouri	$	411	$	197	$	11	$	619
Ameren Illinois	Derivative assets – commodity contracts(a):
	Natural gas	$	2	$	11	$	—	$	13
Liabilities:
Ameren	Derivative liabilities – commodity contracts(a):
	Fuel oils	$	5	$	—	$	—	$	5
	Natural gas	—		13		1		14
	Power	—		1		187		188
	Uranium	—		—		4		4
	Total Ameren	$	5	$	14	$	192	$	211
Ameren Missouri	Derivative liabilities – commodity contracts(a):
	Fuel oils	$	5	$	—	$	—	$	5
	Natural gas	—		6		—		6
	Power	—		1		2		3
	Uranium	—		—		4		4
	Total Ameren Missouri	$	5	$	7	$	6	$	18
Ameren Illinois	Derivative liabilities – commodity contracts(a):
	Natural gas	$	—	$	7	$	1	$	8
	Power	—		—		185		185
	Total Ameren Illinois	$	—	$	7	$	186	$	193

(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, 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):
	Natural gas	$	—	$	1	$	1	$	2
	Power	—		—		16		16
	Total derivative assets – commodity contracts	$	—	$	1	$	17	$	18

		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
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	4	$	—	$	—	$	4
	Equity securities:
	U.S. large capitalization	364		—		—		364
	Debt securities:
	U.S. Treasury and agency securities	—		109		—		109
	Corporate bonds	—		58		—		58
	Other	—		22		—		22
	Total nuclear decommissioning trust fund	$	368	$	189	$	—	$	557	(b)
	Total Ameren	$	368	$	190	$	17	$	575
Ameren Missouri	Derivative assets – commodity contracts(a):
	Natural gas	$	—	$	—	$	1	$	1
	Power	—		—		16		16
	Total derivative assets – commodity contracts	$	—	$	—	$	17	$	17
	Nuclear decommissioning trust fund:
	Cash and cash equivalents	$	4	$	—	$	—	$	4
	Equity securities:
	U.S. large capitalization	364		—		—		364
	Debt securities:
	U.S. Treasury and agency securities	—		109		—		109
	Corporate bonds	—		58		—		58
	Other	—		22		—		22
	Total nuclear decommissioning trust fund	$	368	$	189	$	—	$	557	(b)
	Total Ameren Missouri	$	368	$	189	$	17	$	574
Ameren Illinois	Derivative assets – commodity contracts(a):
	Natural gas	$	—	$	1	$	—	$	1
Liabilities:
Ameren	Derivative liabilities – commodity contracts(a):
	Fuel oils	$	29	$	—	$	—	$	29
	Natural gas	1		62		1		64
	Power	—		—		170		170
	Uranium	—		—		1		1
	Total Ameren	$	30	$	62	$	172	$	264
Ameren Missouri	Derivative liabilities – commodity contracts(a):
	Fuel oils	$	29	$	—	$	—	$	29
	Natural gas	—		13		1		14
	Uranium	—		—		1		1
	Total Ameren Missouri	$	29	$	13	$	2	$	44
Ameren Illinois	Derivative liabilities – commodity contracts(a):
	Natural gas	$	1	$	49	$	—	$	50
	Power	—		—		170		170
	Total Ameren Illinois	$	1	$	49	$	170	$	220

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

(b) Balance excludes $(1) million of receivables, payables, and accrued income, net.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy

The following table summarizes the changes in the fair value of power financial assets and liabilities classified as Level 3 in the fair value hierarchy:

		Net Derivative Commodity Contracts
		Ameren Missouri			Ameren Illinois			Ameren
For the year ended December 31, 2015
Beginning balance at January 1, 2015	$	9		$	(142	)	$	(133	)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:		2			(41	)		(39	)
Purchases		29			—			29
Settlements		(23	)		13			(10	)
Transfers out of Level 3		(1	)		—			(1	)
Ending balance at December 31, 2015	$	16		$	(170	)	$	(154	)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2015	$	—		$	(39	)	$	(39	)
For the year ended December 31, 2016
Beginning balance at January 1, 2016	$	16		$	(170	)	$	(154	)
Realized and unrealized gains (losses) included in regulatory assets/liabilities:		(1	)		(29	)		(30	)
Purchases		13			—			13
Settlements		(21	)		14			(7	)
Ending balance at December 31, 2016	$	7		$	(185	)	$	(178	)
Change in unrealized gains (losses) related to assets/liabilities held at December 31, 2016	$	—		$	(27	)	$	(27	)

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt 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 December 31, 2016 and 2015:

	2016				2015
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Ameren:(a)
Long-term debt and capital lease obligations (including current portion)	$	7,276	$	7,772	$	7,275	$	7,814
Preferred stock	142		131		142		125
Ameren Missouri:
Long-term debt and capital lease obligations (including current portion)	$	3,994	$	4,304	$	4,110	$	4,449
Preferred stock	80		79		80		75
Ameren Illinois:
Long-term debt (including current portion)	$	2,588	$	2,765	$	2,471	$	2,665
Preferred stock	62		52		62		50

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