Supplemental Information (Tables)

3 Months Ended

Mar. 31, 2021

Supplemental Information [Abstract]

Schedule of Cash and Cash Equivalents Including Restricted Cash

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets and the statements of cash flows as of March 31, 2021, and December 31, 2020:

	March 31, 2021						December 31, 2020
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
Cash and cash equivalents	$	6	$	1	$	—	$	139	$	136	$	—
Restricted cash	134		—		125		17		—		6
Restricted cash included in “Other current assets”	—		3		—		—		5		—
Restricted cash included in “Other assets”	24		—		24		141		—		141
Restricted cash included in “Nuclear decommissioning trust fund”	8		8		—		4		4		—
Total cash, cash equivalents, and restricted cash	$	172	$	12	$	149	$	301	$	145	$	147

Schedule of Accounts, Notes, Loans and Financing Receivable

The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the three months ended March 31, 2021 and 2020:

	Three Months
	2021		2020
Ameren:
Beginning of period	$	50	$	17
Bad debt expense	4		3
Net write-offs	(7)		(1)
End of period	$	47	$	19
Ameren Missouri:
Beginning of period	$	16	$	7
Bad debt expense	1		2
Net write-offs	(2)		(1)
End of period	$	15	$	8
Ameren Illinois:(a)
Beginning of Period	$	34	$	10
Bad debt expense	3		1
Net write-offs	(5)		—
End of Period	$	32	$	11

(a)Ameren Illinois has rate-adjustment mechanisms that allow it to recover the difference between its actual net bad debt write-offs under GAAP, including those associated with receivables purchased from alternative retail electric suppliers, and the amount of net bad debt write-offs included in its base rates.

Schedule of Cash Flow, Supplemental Disclosures

Supplemental Cash Flow Information

The following table provides noncash financing and investing activity excluded from the statements of cash flows for the three months ended March 31, 2021 and 2020:

	March 31, 2021						March 31, 2020
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
Investing
Accrued capital expenditures, including wind generation expenditures	$	271	$	141	$	139	$	235	$	97	$	127
Accrued nuclear fuel expenditures	—		—		—		7		7		—
Net realized and unrealized gain (loss) – nuclear decommissioning trust fund	22		22		—		(111)		(111)		—
Financing
Issuance of common stock for stock-based compensation	33		—		—		38		—		—

Asset Retirement Obligation Disclosure

The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the three months ended March 31, 2021:

	Ameren Missouri			Ameren Illinois			Ameren
Balance at December 31, 2020	$	751		$	5	(a)	$	756	(b)
Liabilities incurred (c)	10			—			10
Liabilities settled	(3)			—			(3)
Accretion	8		(d)	—			8		(d)
Change in estimates	(7)		(e)	—			(7)		(e)
Balance at March 31, 2021	$	759		$	5	(a)	$	764	(b)

(a)Included in “Other deferred credits and liabilities” on the balance sheet.

(b)Balance included $59 million and $60 million in “Other current liabilities” on the balance sheet as of March 31, 2021, and December 31, 2020, respectively.

(c)In the first quarter of 2021, Ameren Missouri recorded an ARO related to the decommissioning for the Atchison Renewable Energy Center.

(d)Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.

(e)Ameren Missouri changed its fair value estimate primarily due to a decrease in the cost estimate for closure of certain CCR storage facilities.

Schedule of excise taxes

The following table presents the excise taxes recorded on a gross basis in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” on the statements of income for the three months ended March 31, 2021 and 2020:

	Three Months
	2021		2020
Ameren Missouri	$	31	$	30
Ameren Illinois	39		35
Ameren	$	70	$	65

Schedule of Earnings Per Share, Basic and Diluted

The following table reconciles the basic weighted-average number of common shares outstanding to the diluted weighted-average number of common shares outstanding for the three months ended March 31, 2021 and 2020:

	Three Months
	2021	2020
Weighted-average Common Shares Outstanding – Basic	254.4	246.4
Assumed settlement of performance share units and restricted stock units	1.5	1.1
Dilutive effect of forward sale agreement	—	0.6
Weighted-average Common Shares Outstanding – Diluted(a)	255.9	248.1

(a)There were no potentially dilutive securities excluded from the earnings per diluted share calculations for the three months ended March 31, 2021 and 2020.