Derivative Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2016

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Open Gross Derivative Volumes By Commodity Type

The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of June 30, 2016, and December 31, 2015. As of June 30, 2016, these contracts extended through October 2018, March 2021, May 2032, and January 2019 for fuel oils, natural gas, power, and uranium, respectively.

	Quantity (in millions, except as indicated)
	2016			2015
Commodity	Ameren Missouri	Ameren Illinois	Ameren	Ameren Missouri	Ameren Illinois	Ameren
Fuel oils (in gallons)(a)	24	(b)	24	35	(b)	35
Natural gas (in mmbtu)	30	131	161	30	151	181
Power (in megawatthours)	1	10	11	1	10	11
Uranium (pounds in thousands)	395	(b)	395	494	(b)	494

(a) Consists of ultra-low-sulfur diesel products.

(b) Not applicable.

Derivative Instruments Carrying Value

The following table presents the carrying value and balance sheet location of all derivative commodity contracts, none of which were designated as hedging instruments, as of June 30, 2016, and December 31, 2015:

	Balance Sheet Location	Ameren Missouri		Ameren Illinois		Ameren
2016
Natural gas	Other current assets	$	—	$	2	$	2
	Other assets	1		3		4
Power	Other current assets	15		—		15
	Total assets (a)	$	16	$	5	$	21
Fuel oils	Other current liabilities	$	12	$	—	$	12
	Other deferred credits and liabilities	2		—		2
Natural gas	MTM derivative liabilities	(b)		11		(b)
	Other current liabilities	3		—		14
	Other deferred credits and liabilities	6		6		12
Power	MTM derivative liabilities	(b)		12		(b)
	Other current liabilities	1		—		13
	Other deferred credits and liabilities	—		157		157
Uranium	Other current liabilities	1		—		1
	Other deferred credits and liabilities	3		—		3
	Total liabilities (c)	$	28	$	186	$	214
2015
Natural gas	Other current assets	$	—	$	1	$	1
	Other assets	1		—		1
Power	Other current assets	16		—		16
	Total assets (a)	$	17	$	1	$	18
Fuel oils	Other current liabilities	$	22	$	—	$	22
	Other deferred credits and liabilities	7		—		7
Natural gas	MTM derivative liabilities	(b)		32		(b)
	Other current liabilities	6		—		38
	Other deferred credits and liabilities	8		18		26
Power	MTM derivative liabilities	(b)		13		(b)
	Other current liabilities	—		—		13
	Other deferred credits and liabilities	—		157		157
Uranium	Other current liabilities	1		—		1
	Total liabilities (c)	$	44	$	220	$	264

(a) Because all contracts qualifying for hedge accounting receive regulatory deferral, the cumulative amount of pretax net gains on all derivative instruments is deferred as a regulatory liability.

(b) Balance sheet line item not applicable to registrant.

(c) Because all contracts qualifying for hedge accounting receive regulatory deferral, the cumulative amount of pretax net losses on all derivative instruments is deferred as a regulatory asset.

Offsetting Derivative Assets and Liabilities

The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of June 30, 2016, and December 31, 2015:

			Gross Amounts Not Offset in the Balance Sheet
Commodity Contracts Eligible to be Offset	Gross Amounts Recognized in the Balance Sheet		Derivative Instruments		Cash Collateral Received/Posted(a)		Net Amount
2016
Assets:
Ameren Missouri	$	16	$	2	$	—	$	14
Ameren Illinois	5		4		—		1
Ameren	$	21	$	6	$	—	$	15
Liabilities:
Ameren Missouri	$	28	$	2	$	4	$	22
Ameren Illinois	186		4		—		182
Ameren	$	214	$	6	$	4	$	204
2015
Assets:
Ameren Missouri	$	17	$	1	$	—	$	16
Ameren Illinois	1		—		—		1
Ameren	$	18	$	1	$	—	$	17
Liabilities:
Ameren Missouri	$	44	$	1	$	8	$	35
Ameren Illinois	220		—		3		217
Ameren	$	264	$	1	$	11	$	252

(a) Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Other current assets” and “Other assets” on the balance sheet.

Derivative Instruments With Credit Risk-Related Contingent Features

The following table presents, as of June 30, 2016, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a gross liability position, the cash collateral posted, and the aggregate amount of additional collateral that counterparties could require. The additional collateral required is the net liability position allowed under the master netting arrangements or similar agreements, assuming (1) the credit risk-related contingent features underlying these arrangements were triggered on June 30, 2016, and (2) those counterparties with rights to do so requested collateral.

	Aggregate Fair Value of Derivative Liabilities(a)		Cash Collateral Posted		Potential Aggregate Amount of Additional Collateral Required(b)
2016
Ameren Missouri	$	74	$	2	$	66
Ameren Illinois	50		—		41
Ameren	$	124	$	2	$	107

(a) Before consideration of master netting arrangements or similar agreements and including NPNS and other accrual contract exposures.

(b) As collateral requirements with certain counterparties are based on master netting arrangements or similar agreements, the aggregate amount of additional collateral required to be posted is determined after consideration of the effects of such arrangements.