Derivative Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2017

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, 2017, and December 31, 2016. As of June 30, 2017, these contracts extended through October 2019, March 2023, May 2032, and March 2020 for fuel oils, natural gas, power, and uranium, respectively.

	Quantity (in millions, except as indicated)
	2017			2016
Commodity	Ameren Missouri	Ameren Illinois	Ameren	Ameren Missouri	Ameren Illinois	Ameren
Fuel oils (in gallons)(a)	35	(b)	35	30	(b)	30
Natural gas (in mmbtu)	26	147	173	25	129	154
Power (in megawatthours)	1	9	10	1	9	10
Uranium (pounds in thousands)	445	(b)	445	345	(b)	345

(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, 2017, and December 31, 2016:

	Balance Sheet Location	Ameren Missouri			Ameren Illinois		Ameren
2017
Fuel oils	Other current assets	$	1		$	—	$	1
Natural gas	Other current assets	—			1		1
	Other assets	—			1		1
Power	Other current assets	14			—		14
	Other assets	1			—		1
	Total assets (a)	$	16		$	2	$	18
Fuel oils	Other current liabilities	$	5		$	—	$	5
	Other deferred credits and liabilities	1			—		1
Natural gas	Other current liabilities	2			9		11
	Other deferred credits and liabilities	5			6		11
Power	Other current liabilities	1			13		14
	Other deferred credits and liabilities	—			179		179
Uranium	Other deferred credits and liabilities	—		(b)	—		—		(b)
	Total liabilities (c)	$	14		$	207	$	221
2016
Fuel oils	Other current assets	$	2		$	—	$	2
	Other assets	1			—		1
Natural gas	Other current assets	1			11		12
	Other assets	1			2		3
Power	Other current assets	9			—		9
	Total assets (a)	$	14		$	13	$	27
Fuel oils	Other current liabilities	$	5		$	—	$	5
Natural gas	Other current liabilities	1			3		4
	Other deferred credits and liabilities	5			5		10
Power	Other current liabilities	3			12		15
	Other deferred credits and liabilities	—			173		173
Uranium	Other deferred credits and liabilities	4			—		4
	Total liabilities (c)	$	18		$	193	$	211

(a) The cumulative amount of pretax net gains on all derivative instruments is deferred as a regulatory liability.

(b) Beginning in 2017, as a result of rulebook amendments at the Chicago Mercantile Exchange, the fair value of uranium derivative liabilities are offset by certain settlement payments made to the exchange previously characterized as collateral and included within “Other assets” on Ameren’s and Ameren Missouri’s balance sheet.

(c) The cumulative amount of pretax net losses on all derivative instruments is deferred as a regulatory asset.

Derivative Instruments With Credit Risk-Related Contingent Features

The following table presents, as of June 30, 2017, 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, 2017, 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)
2017
Ameren Missouri	$	65	$	3	$	59
Ameren Illinois	43		—		37
Ameren	$	108	$	3	$	96

(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.