Derivative Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2022

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 December 31, 2022 and 2021. As of December 31, 2022, these contracts extended through October 2024, March 2029, May 2032, and March 2024 for fuel oils, natural gas, power, and uranium, respectively.

	Quantity (in millions, except as indicated)
	2022			2021
Commodity	Ameren Missouri	Ameren Illinois	Ameren	Ameren Missouri	Ameren Illinois	Ameren
Fuel oils (in gallons)	18	—	18	30	—	30
Natural gas (in mmbtu)	48	157	205	35	144	179
Power (in MWhs)	1	6	7	6	6	12
Uranium (pounds in thousands)	514	—	514	586	—	586

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 December 31, 2022 and 2021:

		2022						2021
Commodity	Balance Sheet Location	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren
Fuel oils	Other current assets	$	13	$	—	$	13		$	8	$	—	$	8
	Other assets	3		—		3			5		—		5
Natural gas	Other current assets	7		23		30			7		28		35
	Other assets	9		11		20			5		13		18
Power	Other current assets	14		2		16			23		—		23
	Other assets	—		4		4			—		—		—
Uranium	Other current assets	2		—		2			—		—		—
	Other assets	1		—		1			1		—		1
	Total assets	$	49	$	40	$	89		$	49	$	41	$	90
Natural gas	Other current liabilities	7		20		27			2		6		8
	Other deferred credits and liabilities	2		9		11			1		2		3
Power	Other current liabilities	59		2		61			50		9		59
	Other deferred credits and liabilities	—		37		37			23		108		131
Uranium	Other current liabilities	—		—		—			1		—		1
	Total liabilities	$	68	$	68	$	136		$	77	$	125	$	202

Offsetting 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 December 31, 2022 and 2021:

			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
2022
Assets:
Ameren Missouri	$	49	$	9	$	—	$	40
Ameren Illinois	40		20		—		20
Ameren	$	89	$	29	$	—	$	60
Liabilities:
Ameren Missouri	$	68	$	9	$	56	$	3
Ameren Illinois	68		20		—		48
Ameren	$	136	$	29	$	56	$	51
2021
Assets:
Ameren Missouri	$	49	$	15	$	—	$	34
Ameren Illinois	41		4		—		37
Ameren	$	90	$	19	$	—	$	71
Liabilities:
Ameren Missouri	$	77	$	15	$	47	$	15
Ameren Illinois	125		4		—		121
Ameren	$	202	$	19	$	47	$	136

(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 “Current collateral assets” and “Other assets” on the balance sheet for Ameren and Ameren Missouri and “Other current assets” and “Other assets” for Ameren Illinois.