Ameren Illinois (AILIN) 10-Q 5 Aug 22 2022 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2022	Jul. 29, 2022
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2022
Document Transition Report	false
Entity File Number	1-14756
Entity Registrant Name	Ameren Corporation
Entity Tax Identification Number	43-1723446
Entity Incorporation, State or Country Code	MO
Entity Address, Address Line One	1901 Chouteau Avenue
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63103
City Area Code	(314)
Local Phone Number	621-3222
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol(s)	AEE
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Shares outstanding		258,370,605
Entity Central Index Key	0001002910
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Amendment Flag	false
Union Electric Company
Entity Information [Line Items]
Entity File Number	1-2967
Entity Registrant Name	Union Electric Company
Entity Tax Identification Number	43-0559760
Entity Incorporation, State or Country Code	MO
Entity Address, Address Line One	1901 Chouteau Avenue
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63103
City Area Code	(314)
Local Phone Number	621-3222
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Shares outstanding		102,123,834
Entity Central Index Key	0000100826
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Amendment Flag	false
Ameren Illinois Company
Entity Information [Line Items]
Entity File Number	1-3672
Entity Registrant Name	Ameren Illinois Company
Entity Tax Identification Number	37-0211380
Entity Incorporation, State or Country Code	IL
Entity Address, Address Line One	10 Executive Drive
Entity Address, City or Town	Collinsville
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	62234
City Area Code	(618)
Local Phone Number	343-8150
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Shares outstanding		25,452,373
Entity Central Index Key	0000018654
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Amendment Flag	false

Consolidated Statement of Incom

Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating Revenues:
Total operating revenues	$ 1,726	$ 1,472	$ 3,605	$ 3,038
Operating Expenses:
Fuel	83	173	259	238
Purchased power	318	129	495	320
Natural gas purchased for resale	80	65	373	230
Other operations and maintenance	491	412	952	832
Depreciation and amortization	316	285	615	566
Taxes other than income taxes	129	122	271	250
Total operating expenses	1,417	1,186	2,965	2,436
Operating Income	309	286	640	602
Other Income, Net	62	49	122	95
Interest Charges	126	96	230	196
Income Before Income Taxes	245	239	532	501
Income Taxes	36	31	70	58
Net Income	209	208	462	443
Less: Net Income Attributable to Noncontrolling Interests	2	1	3	3
Net Income Attributable to Ameren Common Shareholders	207	207	459	440
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	0	(1)	1	0
Comprehensive Income	209	207	463	443
Less: Comprehensive Income Attributable to Noncontrolling Interests	2	1	3	3
Comprehensive Income Attributable to Ameren Common Shareholders	$ 207	$ 206	$ 460	$ 440
Earnings Per Share, Basic and Diluted [Abstract]
Earnings per Common Share – Basic	$ 0.80	$ 0.81	$ 1.78	$ 1.72
Earnings per Common Share – Diluted	$ 0.80	$ 0.80	$ 1.77	$ 1.71
Weighted-average Common Shares Outstanding – Basic	258.2	256.1	258	255.2
Weighted-average Common Shares Outstanding – Diluted	259.4	257.2	259.2	256.5
Electric
Operating Revenues:
Total operating revenues	$ 1,513	$ 1,284	$ 2,831	$ 2,440
Natural gas
Operating Revenues:
Total operating revenues	213	188	774	598
Union Electric Company
Operating Revenues:
Total operating revenues	919	809	1,737	1,513
Operating Expenses:
Fuel	83	173	259	238
Purchased power	161	50	211	138
Natural gas purchased for resale	12	5	58	36
Other operations and maintenance	260	218	492	443
Depreciation and amortization	178	157	342	313
Taxes other than income taxes	90	85	175	162
Total operating expenses	784	688	1,537	1,330
Operating Income	135	121	200	183
Other Income, Net	24	24	47	47
Interest Charges	60	36	99	75
Income Before Income Taxes	99	109	148	155
Income Taxes	(2)	(3)	(4)	(5)
Net Income	101	112	152	160
Preferred Stock Dividends	1	1	2	2
Net Income Attributable to Parent	100	111	150	158
Union Electric Company | Electric
Operating Revenues:
Total operating revenues	890	789	1,628	1,430
Union Electric Company | Natural gas
Operating Revenues:
Total operating revenues	29	20	109	83
Ameren Illinois Company
Operating Revenues:
Total operating revenues	769	629	1,793	1,452
Operating Expenses:
Purchased power	158	84	289	190
Natural gas purchased for resale	68	60	315	194
Other operations and maintenance	225	193	448	387
Depreciation and amortization	128	117	252	232
Taxes other than income taxes	35	34	88	80
Total operating expenses	614	488	1,392	1,083
Operating Income	155	141	401	369
Other Income, Net	25	16	49	30
Interest Charges	41	40	83	82
Income Before Income Taxes	139	117	367	317
Income Taxes	35	31	94	81
Net Income	104	86	273	236
Preferred Stock Dividends	1	0	1	1
Net Income Attributable to Parent	103	86	272	235
Ameren Illinois Company | Electric
Operating Revenues:
Total operating revenues	585	461	1,128	937
Ameren Illinois Company | Natural gas
Operating Revenues:
Total operating revenues	$ 184	$ 168	$ 665	$ 515

Consolidated Statement of Inc_2

Consolidated Statement of Income (Loss) and Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Pension and other postretirement benefit plan activity, tax	$ 0	$ 0	$ 0	$ 0

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Current Assets:
Cash and cash equivalents	$ 7	$ 8
Accounts receivable - trade (less allowance for doubtful accounts)	519	434
Unbilled revenue	400	301
Miscellaneous accounts receivable	81	85
Inventories	600	592
Mark-to-market derivative assets	157	66
Current regulatory assets	333	319
Current collateral assets	222	66
Other current assets	77	97
Total current assets	2,396	1,968
Property, Plant, and Equipment, Net	30,086	29,261
Investments and Other Assets:
Nuclear decommissioning trust fund	957	1,159
Goodwill	411	411
Regulatory assets	1,487	1,289
Pension and other postretirement benefits	808	756
Other assets	963	891
Total investments and other assets	4,626	4,506
TOTAL ASSETS	37,108	35,735
Current Liabilities:
Current maturities of long-term debt	605	505
Short-term debt	1,021	545
Accounts and wages payable	897	1,095
Current regulatory liabilities	241	113
Other current liabilities	824	568
Total current liabilities	3,588	2,826
Long-term Debt, Net	12,985	12,562
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	3,614	3,499
Regulatory liabilities	5,727	5,848
Asset retirement obligations	774	757
Other deferred credits and liabilities	411	414
Total deferred credits and other liabilities	10,526	10,518
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	3	3
Other paid-in capital, principally premium on common stock	6,527	6,502
Retained earnings	3,336	3,182
Accumulated other comprehensive income	14	13
Total shareholders’ equity	9,880	9,700
Noncontrolling Interests	129	129
Total equity	10,009	9,829
TOTAL LIABILITIES AND EQUITY	37,108	35,735
Union Electric Company
Current Assets:
Cash and cash equivalents	0	0
Accounts receivable - trade (less allowance for doubtful accounts)	201	190
Accounts receivable – affiliates	55	44
Unbilled revenue	244	142
Miscellaneous accounts receivable	50	71
Inventories	426	419
Mark-to-market derivative assets	89	38
Current regulatory assets	232	127
Current collateral assets	199	66
Other current assets	23	38
Total current assets	1,519	1,135
Property, Plant, and Equipment, Net	15,635	15,296
Investments and Other Assets:
Nuclear decommissioning trust fund	957	1,159
Regulatory assets	640	523
Pension and other postretirement benefits	225	208
Other assets	425	401
Total investments and other assets	2,247	2,291
TOTAL ASSETS	19,401	18,722
Current Liabilities:
Current maturities of long-term debt	55	55
Short-term debt	285	165
Accounts and wages payable	388	631
Accounts payable – affiliates	37	46
Taxes accrued	134	34
Interest accrued	75	60
Mark-to-market derivative liabilities	145	53
Current regulatory liabilities	130	57
Other current liabilities	134	116
Total current liabilities	1,383	1,217
Long-term Debt, Net	6,084	5,564
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	1,901	1,852
Regulatory liabilities	3,121	3,354
Asset retirement obligations	770	753
Other deferred credits and liabilities	81	71
Total deferred credits and other liabilities	5,873	6,030
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	511	511
Other paid-in capital, principally premium on common stock	2,725	2,725
Preferred stock	80	80
Retained earnings	2,745	2,595
Total shareholders’ equity	6,061	5,911
TOTAL LIABILITIES AND EQUITY	19,401	18,722
Ameren Illinois Company
Current Assets:
Cash and cash equivalents	0	0
Accounts receivable - trade (less allowance for doubtful accounts)	302	228
Accounts receivable – affiliates	9	24
Unbilled revenue	156	159
Miscellaneous accounts receivable	16	1
Inventories	174	173
Mark-to-market derivative assets	68	28
Current regulatory assets	94	180
Other current assets	46	30
Total current assets	865	823
Property, Plant, and Equipment, Net	12,688	12,223
Investments and Other Assets:
Goodwill	411	411
Regulatory assets	828	752
Pension and other postretirement benefits	449	427
Other assets	478	399
Total investments and other assets	2,166	1,989
TOTAL ASSETS	15,719	15,035
Current Liabilities:
Current maturities of long-term debt	500	400
Short-term debt	141	103
Accounts and wages payable	428	361
Accounts payable – affiliates	118	64
Current regulatory liabilities	111	54
Other current liabilities	277	251
Total current liabilities	1,575	1,233
Long-term Debt, Net	3,894	3,992
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	1,626	1,558
Regulatory liabilities	2,484	2,374
Other deferred credits and liabilities	228	238
Total deferred credits and other liabilities	4,338	4,170
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	0	0
Other paid-in capital, principally premium on common stock	2,914	2,914
Preferred stock	49	49
Retained earnings	2,949	2,677
Total shareholders’ equity	5,912	5,640
TOTAL LIABILITIES AND EQUITY	$ 15,719	$ 15,035

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Accounts Receivable, Allowance for Credit Loss, Current	$ 30	$ 29
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common Stock, Shares, Outstanding	258,400,000	257,700,000
Union Electric Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 12	$ 13
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common Stock, Shares, Outstanding	102,100,000	102,100,000
Ameren Illinois Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 18	$ 16
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	45,000,000	45,000,000
Common Stock, Shares, Outstanding	25,500,000	25,500,000

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash Flows From Operating Activities:
Net income	$ 462	$ 443
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	665	596
Amortization of nuclear fuel	28	20
Amortization of debt issuance costs and premium/discounts	12	11
Deferred income taxes and investment tax credits, net	66	59
Allowance for equity funds used during construction	(19)	(16)
Stock-based compensation costs	12	11
Other	33	2
Changes in assets and liabilities:
Receivables	(187)	(92)
Inventories	(8)	(5)
Accounts and wages payable	(87)	(208)
Taxes accrued	94	104
Regulatory assets and liabilities	(74)	(441)
Assets, other	(35)	(36)
Liabilities, other	45	13
Pension and other postretirement benefits	(32)	1
Counterparty collateral, net	(103)	(26)
Net cash provided by operating activities	872	436
Cash Flows From Investing Activities:
Capital expenditures	(1,538)	(1,763)
Nuclear fuel expenditures	(22)	(4)
Purchases of securities – nuclear decommissioning trust fund	(122)	(203)
Sales and maturities of securities – nuclear decommissioning trust fund	114	208
Other	16	2
Net cash used in investing activities	(1,552)	(1,760)
Cash Flows From Financing Activities:
Dividends on common stock	(305)	(282)
Dividends paid to noncontrolling interest holders	(3)	(3)
Short-term debt, net	475	(59)
Issuances of long-term debt	524	1,423
Issuances of common stock	17	258
Redemptions of Ameren Illinois preferred stock	0	(13)
Employee payroll taxes related to stock-based compensation	(16)	(17)
Debt issuance costs	(6)	(13)
Other	0	(4)
Net cash provided by financing activities	686	1,290
Net change in cash, cash equivalents, and restricted cash	6	(34)
Cash, cash equivalents, and restricted cash at beginning of year	155	301
Cash, cash equivalents, and restricted cash at end of period	161	267
Union Electric Company
Cash Flows From Operating Activities:
Net income	152	160
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	393	343
Amortization of nuclear fuel	28	20
Amortization of debt issuance costs and premium/discounts	3	3
Deferred income taxes and investment tax credits, net	19	(2)
Allowance for equity funds used during construction	(10)	(10)
Other	4	6
Changes in assets and liabilities:
Receivables	(105)	(135)
Inventories	(7)	(8)
Accounts and wages payable	(159)	(172)
Taxes accrued	81	167
Regulatory assets and liabilities	(128)	(165)
Assets, other	12	23
Liabilities, other	24	19
Pension and other postretirement benefits	(8)	5
Counterparty collateral, net	(118)	(30)
Net cash provided by operating activities	181	224
Cash Flows From Investing Activities:
Capital expenditures	(806)	(1,101)
Nuclear fuel expenditures	(22)	(4)
Purchases of securities – nuclear decommissioning trust fund	(122)	(203)
Sales and maturities of securities – nuclear decommissioning trust fund	114	208
Proceeds from Collection of Advance to Affiliate	0	47
Other	18	0
Net cash used in investing activities	(818)	(1,053)
Cash Flows From Financing Activities:
Dividends on preferred stock	(2)	(2)
Short-term debt, net	120	0
Issuances of long-term debt	524	524
Capital contributions from parent	0	183
Debt issuance costs	(6)	(4)
Net cash provided by financing activities	636	701
Net change in cash, cash equivalents, and restricted cash	(1)	(128)
Cash, cash equivalents, and restricted cash at beginning of year	8	145
Cash, cash equivalents, and restricted cash at end of period	7	17
Ameren Illinois Company
Cash Flows From Operating Activities:
Net income	273	236
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	251	231
Amortization of debt issuance costs and premium/discounts	6	6
Deferred income taxes and investment tax credits, net	55	84
Allowance for equity funds used during construction	(9)	(6)
Other	6	5
Changes in assets and liabilities:
Receivables	(76)	43
Inventories	(1)	3
Accounts and wages payable	76	(23)
Taxes accrued	62	36
Regulatory assets and liabilities	55	(273)
Assets, other	(66)	(46)
Liabilities, other	61	(2)
Pension and other postretirement benefits	(18)	(8)
Net cash provided by operating activities	675	286
Cash Flows From Investing Activities:
Capital expenditures	(699)	(646)
Payments for Advance to Affiliate	0	(20)
Other	0	(2)
Net cash used in investing activities	(699)	(668)
Cash Flows From Financing Activities:
Dividends on preferred stock	(1)	(1)
Short-term debt, net	38	0
Money pool borrowings, net	0	(19)
Issuances of long-term debt	0	449
Capital contributions from parent	0	70
Redemption of preferred stock	0	(13)
Debt issuance costs	0	(5)
Other	0	(4)
Net cash provided by financing activities	37	477
Net change in cash, cash equivalents, and restricted cash	13	95
Cash, cash equivalents, and restricted cash at beginning of year	133	147
Cash, cash equivalents, and restricted cash at end of period	$ 146	$ 242

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital	Retained Earnings	Deferred Retirement Benefit Costs	Accumulated Other Comprehensive Income	Total Ameren Corporation Shareholders' Equity	Noncontrolling Interests	Union Electric Company	Union Electric Company Common Stock	Union Electric Company Other Paid-in Capital	Union Electric Company Preferred Stock	Union Electric Company Retained Earnings	Ameren Illinois Company	Ameren Illinois Company Common Stock	Ameren Illinois Company Other Paid-in Capital	Ameren Illinois Company Preferred Stock	Ameren Illinois Company Retained Earnings
Beginning of period at Dec. 31, 2020			$ 6,179	$ 2,757	$ (1)			$ 142			$ 2,518		$ 2,101			$ 2,652	$ 62	$ 2,252
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			113
Shares issued under the ATM program			121
Shares issued under the DRPlus and 401(k) plan			24
Stock-based compensation activity			(1)
Capital contributions from parent									$ 183		183			$ 70		70
Net income	$ 443								160				160	236				236
Net income attributable to Ameren common shareholders	440			440
Dividends on common stock				(282)
Preferred stock dividends													(2)					(1)
Change in deferred retirement benefit costs	0				0
Net income attributable to noncontrolling interest holders	$ (3)							3
Dividends paid to noncontrolling interest holders								(3)
Redemptions of preferred stock								(13)									(13)
Common stock shares outstanding at beginning of year (in shares) at Dec. 31, 2020	253,300,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	1,600,000
Stock Issued During Period, Shares, New Issues	1,400,000
Shares issued under the DRPlus and 401(k) plan	300,000
Shares issued for stock-based compensation (in shares)	500,000
Common stock shares outstanding at end of period (in shares) at Jun. 30, 2021	257,100,000
End of period at Jun. 30, 2021	$ 9,482	$ 3	6,436	2,915	(1)	$ (1)		129		$ 511	2,701	$ 80	2,259		$ 0	2,722	49	2,487
Shareholders' equity, end of year at Jun. 30, 2021							$ 9,353		5,551					5,258
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 1.10
Beginning of period at Mar. 31, 2021			6,295	2,850	0			129			2,631		2,148			2,692	49	2,401
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			0
Shares issued under the ATM program			121
Shares issued under the DRPlus and 401(k) plan			12
Stock-based compensation activity			8
Capital contributions from parent											70					30
Net income	$ 208								112				112	86				86
Net income attributable to Ameren common shareholders	207			207
Dividends on common stock				(142)
Preferred stock dividends													(1)					0
Change in deferred retirement benefit costs	(1)				(1)
Net income attributable to noncontrolling interest holders	$ (1)							1
Dividends paid to noncontrolling interest holders								(1)
Redemptions of preferred stock								0									0
Common stock shares outstanding at beginning of year (in shares) at Mar. 31, 2021	255,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	0
Stock Issued During Period, Shares, New Issues	1,400,000
Shares issued under the DRPlus and 401(k) plan	200,000
Shares issued for stock-based compensation (in shares)	0
Common stock shares outstanding at end of period (in shares) at Jun. 30, 2021	257,100,000
End of period at Jun. 30, 2021	$ 9,482	3	6,436	2,915	(1)	(1)		129		511	2,701	80	2,259		0	2,722	49	2,487
Shareholders' equity, end of year at Jun. 30, 2021							9,353		5,551					5,258
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 0.55
Beginning of period at Dec. 31, 2021	$ 9,829		6,502	3,182	13			129			2,725		2,595			2,914	49	2,677
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			0
Shares issued under the ATM program			0
Shares issued under the DRPlus and 401(k) plan			25
Stock-based compensation activity			0
Capital contributions from parent									0		0			0		0
Net income	462								$ 152				152	$ 273				273
Net income attributable to Ameren common shareholders	459			459
Dividends on common stock				(305)
Preferred stock dividends													(2)					(1)
Change in deferred retirement benefit costs	1				1
Net income attributable to noncontrolling interest holders	$ (3)							3
Dividends paid to noncontrolling interest holders								(3)
Redemptions of preferred stock								0									0
Common stock shares outstanding at beginning of year (in shares) at Dec. 31, 2021	257,700,000								102,100,000					25,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	0
Stock Issued During Period, Shares, New Issues	0
Shares issued under the DRPlus and 401(k) plan	300,000
Shares issued for stock-based compensation (in shares)	400,000
Common stock shares outstanding at end of period (in shares) at Jun. 30, 2022	258,400,000								102,100,000					25,500,000
End of period at Jun. 30, 2022	$ 10,009	3	6,527	3,336	14	14		129		511	2,725	80	2,745		0	2,914	49	2,949
Shareholders' equity, end of year at Jun. 30, 2022	$ 9,880						9,880		$ 6,061					$ 5,912
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 1.18
Beginning of period at Mar. 31, 2022			6,507	3,282	14			129			2,725		2,645			2,914	49	2,846
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			0
Shares issued under the ATM program			0
Shares issued under the DRPlus and 401(k) plan			12
Stock-based compensation activity			8
Capital contributions from parent											0					0
Net income	$ 209								$ 101				101	$ 104				104
Net income attributable to Ameren common shareholders	207			207
Dividends on common stock				(153)
Preferred stock dividends													(1)					(1)
Change in deferred retirement benefit costs	0				0
Net income attributable to noncontrolling interest holders	$ (2)							2
Dividends paid to noncontrolling interest holders								(2)
Redemptions of preferred stock								0									0
Common stock shares outstanding at beginning of year (in shares) at Mar. 31, 2022	258,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	0
Stock Issued During Period, Shares, New Issues	0
Shares issued under the DRPlus and 401(k) plan	200,000
Shares issued for stock-based compensation (in shares)	0
Common stock shares outstanding at end of period (in shares) at Jun. 30, 2022	258,400,000								102,100,000					25,500,000
End of period at Jun. 30, 2022	$ 10,009	$ 3	$ 6,527	$ 3,336	$ 14	$ 14		$ 129		$ 511	$ 2,725	$ 80	$ 2,745		$ 0	$ 2,914	$ 49	$ 2,949
Shareholders' equity, end of year at Jun. 30, 2022	$ 9,880						$ 9,880		$ 6,061					$ 5,912
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 0.59

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES General Ameren, headquartered in St. Louis, Missouri, is a public utility holding company whose primary assets are its equity interests in its subsidiaries. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below. Ameren has other subsidiaries that conduct other activities, such as providing shared services. • Union Electric Company, doing business as Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri. • Ameren Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois. • ATXI operates a FERC rate-regulated electric transmission business in the MISO. The COVID-19 pandemic continues to affect our results of operations, financial position, and liquidity. While our electric sales volumes, excluding the estimated effects of weather and customer energy-efficiency programs, increased in the first six months of 2022, compared to the same period in 2021, they were comparable to pre-pandemic levels at Ameren Missouri and remain below pre-pandemic levels at Ameren Illinois. However, revenues from Ameren Illinois’ electric distribution business, residential and small nonresidential customers of Ameren Illinois’ natural gas distribution business, and Ameren Illinois’ and ATXI’s electric transmission businesses are decoupled from changes in sales volumes. Earnings at Ameren Missouri and those associated with Ameren Illinois’ large nonresidential natural gas customers are exposed to such changes. There has also been a shift in sales volumes by customer class at both Ameren Missouri and Ameren Illinois, which began in 2020, with an increase in residential sales, and a decrease in commercial and industrial sales. The continued effect of the COVID-19 pandemic on our results of operations, financial position, and liquidity in subsequent periods will depend on its severity and longevity, future regulatory or legislative actions with respect thereto, and the resulting impact on business, economic, and capital market conditions. Ameren’s and Ameren Missouri’s financial statements are prepared on a consolidated basis and therefore include the accounts of their majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri’s subsidiaries were created for the ownership of renewable generation projects. Ameren Illinois has no subsidiaries. All tabular dollar amounts are in millions, unless otherwise indicated. Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Form 10-K. Variable Interest Entities As of June 30, 2022, and December 31, 2021, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $61 million and $56 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Any earnings or losses related to these investments are included in “Other Income, Net” on Ameren’s consolidated statement of income and comprehensive income. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly affect the activities of these variable interest entities. As of June 30, 2022, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $61 million plus associated outstanding funding commitments of $22 million. Company-owned Life Insurance Ameren and Ameren Illinois have company-owned life insurance, which is recorded at the net cash surrender value. The net cash surrender value is the amount that can be realized under the insurance policies at the balance sheet date. As of June 30, 2022, the cash surrender value of company-owned life insurance at Ameren and Ameren Illinois was $244 million (December 31, 2021 – $278 million) and $115 million (December 31, 2021 – $117 million), respectively, while total borrowings against the policies were $108 million (December 31, 2021 – $109 million) at both Ameren and Ameren Illinois. Ameren and Ameren Illinois have the right to offset the borrowings against the cash surrender value of the policies and, consequently, present the net asset in “Other assets” on their respective balance sheets. The net cash surrender value of Ameren’s company-owned life insurance is affected by the investment performance of a separate account in which Ameren holds a beneficial interest.

Rate And Regulatory Matters

Rate And Regulatory Matters	6 Months Ended
	Jun. 30, 2022
Public Utilities, General Disclosures [Abstract]
RATE AND REGULATORY MATTERS	RATE AND REGULATORY MATTERS Below is a summary of updates to significant regulatory proceedings and related legal proceedings. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K for additional information and a summary of our regulatory frameworks. We are unable to predict the ultimate outcome of these matters, the timing of final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity. Missouri 2022 Electric Service Regulatory Rate Review In August 2022, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service by $316 million. The electric rate increase request is based on a 10.2% ROE, a capital structure composed of 51.9% common equity, a rate base of $11.6 billion, and a test year ended March 31, 2022, with certain pro-forma adjustments expected through an anticipated true-up date of December 31, 2022. Ameren Missouri also requested the continued use of the FAC and trackers for pension and postretirement benefits, uncertain income tax positions, certain excess deferred income taxes, and renewable energy standard costs that the MoPSC previously authorized in earlier electric rate orders, as well as the use of an electric property tax tracker allowed under Missouri Senate Bill 745 discussed below. The electric rate increase request reflects the following: • increased infrastructure investments made under Ameren Missouri’s Smart Energy Plan, including increased cost of capital and depreciation expense; • increased net fuel expense due to reduced off system sales, primarily driven by expected reduced operations at the Rush Island Energy Center; and • extending the retirement date of the Sioux Energy Center from 2028 to 2030, consistent with Ameren Missouri’s 2022 Change to the 2020 IRP, in order to ensure reliability during the transition to clean energy generation. In connection with the planned accelerated retirement of the Rush Island Energy Center, Ameren Missouri expects to seek approval from the MoPSC to finance the costs associated with the retirement, including the remaining unrecovered net plant balance associated with the facility, through the issuance of securitized utility tariff bonds pursuant to the Missouri securitization statute. As such, Ameren Missouri did not request a change in the depreciation rates related to the Rush Island Energy Center in this electric service regulatory rate review. The MoPSC proceeding relating to the proposed electric service rate changes will take place over a period of up to 11 months, with a decision by the MoPSC expected by June 2023 and new rates effective by July 2023. Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve, whether the requested regulatory recovery mechanisms will be approved, or whether any rate change that may eventually be approved will be sufficient for Ameren Missouri to recover its costs and earn a reasonable return on its investments when the rate change goes into effect. Missouri Senate Bill 745 In June 2022, Missouri Senate Bill 745 was enacted and will become effective on August 28, 2022. The law extended Ameren Missouri’s PISA election through December 2028 and allows for an additional five-year extension through December 2033 if requested by Ameren Missouri and approved by the MoPSC, among other things. The law established a 2.5% annual limit on increases to the electric service revenue requirement used to set customer rates due to the inclusion of incremental PISA deferrals in the revenue requirement. The limitation will be effective for revenue requirements approved by the MoPSC after January 1, 2024, and will be based on the revenue requirement established in the immediately preceding rate order. The current rate limitation, which is effective through 2023, is a 2.85% cap on the compound annual growth rate in the average overall customer rate per kilowatthour, based on the electric rates that became effective in April 2017, less half of the annual savings from the TCJA that was passed on to customers as approved in a July 2018 MoPSC order. The law also established electric and natural gas property tax trackers that allow Ameren Missouri to defer the difference between actual property taxes incurred and related taxes included in customer rates as a regulatory asset or regulatory liability, with the difference expected to be reflected in rate base in a subsequent rate order. Solar Generation Facilities In February 2022, Ameren Missouri, through a subsidiary, entered into a build-transfer agreement to acquire, after construction, a 150-MW solar generation facility, which is expected to be located in southeastern Illinois and, if approved by the MoPSC, serve customers under Ameren Missouri’s Renewable Solutions Program discussed below. In June 2022, Ameren Missouri, through a subsidiary, entered into a build-transfer agreement to acquire, after construction, a 200-MW solar generation facility, which is expected to be located in central Missouri and support Ameren Missouri’s compliance with the state of Missouri’s requirement of achieving 15% of retail sales from renewable energy sources, of which 2% must be derived from solar energy sources. The acquisitions are aligned with the 2022 Change to the 2020 IRP, which Ameren Missouri filed with the MoPSC in June 2022, and are subject to certain conditions, including the issuance of certificates of convenience and necessity by the MoPSC, obtaining MISO transmission interconnection agreements, and approval by the FERC. In July 2022, Ameren Missouri filed for certificates of convenience and necessity with the MoPSC for both facilities and expects decisions by March 2023 and April 2023 for the 200-MW facility and the 150-MW facility, respectively. Depending on the timing of regulatory approvals and the impact of potential sourcing issues resulting from a Department of Commerce investigation of solar panels imported from four Southeast Asian countries initiated in late March 2022 and the detention of certain solar panels sourced from China as a result of the Uyghur Forced Labor Prevention Act that was passed in December 2021, the projects could be completed as early as the fourth quarter of 2024. Renewable Solutions Program In July 2022, Ameren Missouri filed a request with the MoPSC seeking approval of its Renewable Solutions Program and a tariff related to participation in the program. The program would allow certain commercial, industrial, and governmental customers to receive up to 100% of their energy from renewable resources. Based on customer contracts, the program would enable Ameren Missouri to supply renewable solar energy generated by the 150-MW facility discussed above to customers that enroll in the program. MoPSC Staff Review of Planned Rush Island Energy Center Retirement In February 2022, the MoPSC issued an order directing the MoPSC staff to review Ameren Missouri’s planned accelerated retirement of the Rush Island Energy Center as a result of the NSR and Clean Air Act Litigation discussed in Note 9 – Commitments and Contingencies. The MoPSC staff’s review includes potential impacts on the reliability and cost of Ameren Missouri’s service to its customers; Ameren Missouri’s plans to mitigate the customer impacts of the accelerated retirement; and the prudence of Ameren Missouri’s actions and decisions with regard to the Rush Island Energy Center, which is expected to be addressed in the current electric service regulatory rate review, among other things. In April 2022, the MoPSC staff filed an initial report with the MoPSC in which the staff concluded early retirement of the Rush Island Energy Center may cause reliability concerns. The MoPSC staff is under no deadline to complete this review. Ameren Missouri is unable to predict the results of this matter. Results of the review could be used in other MoPSC proceedings, which could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. December 2021 MoPSC Electric and Natural Gas Rate Orders In December 2021, the MoPSC issued orders in Ameren Missouri’s 2021 electric service and natural gas delivery service regulatory rate reviews. The new electric and natural gas rates approved by these orders went into effect on February 28, 2022. Illinois MYRP ROE Performance Metrics Under an MYRP, the ROE approved by the ICC would be subject to annual adjustments during the four-year period based on certain performance metrics, with aggregate symmetrical performance-based ROE incentives and penalties ranging from 20 to 60 basis points annually. In January 2022, Ameren Illinois filed a request with the ICC proposing performance metrics that would be used in determining ROE incentives and penalties. In April 2022, Ameren Illinois filed a revised request proposing total ROE incentives and penalties of 24 basis points, allocated evenly among eight proposed performance metrics. In May 2022, the ICC staff recommended that the ICC allow ROE incentives and penalties of no less than 20 basis points and no more than 24 basis points, allocated evenly across the number of performance metrics ultimately approved by the ICC. The ICC is required to issue an order on this matter by September 30, 2022. Electric Distribution Service Rates Under IEIMA In April 2022, Ameren Illinois filed its annual electric distribution service performance-based formula rate update with the ICC to be used for 2023 rates. In July 2022, Ameren Illinois filed a revised request seeking to increase its annual revenues for electric distribution service by $84 million. The updated request reflects an increase to the annual performance-based formula rate based on 2021 actual recoverable costs and expected net plant additions for 2022, an increase to include the 2021 revenue requirement reconciliation adjustment including a capital structure composed of 54% common equity, and a decrease for the conclusion of the 2020 revenue requirement reconciliation adjustment, which will be fully collected from customers in 2022, consistent with the ICC’s December 2021 annual update filing order. In June 2022, the ICC staff submitted its calculation of the revenue requirement included in Ameren Illinois’ update filing, recommending a $60 million increase in Ameren Illinois’ electric distribution service rates, which is based on a capital structure composed of 50% common equity. An ICC decision in this proceeding is required by December 2022, with new rates effective in January 2023. Electric Customer Energy-Efficiency Investments In June 2022, Ameren Illinois filed its annual electric customer energy-efficiency formula rate update to increase its rates by $17 million with the ICC. An ICC decision in this proceeding is required by December 2022, with new rates effective January 2023. In June 2022, the ICC issued an order approving Ameren Illinois’ revised energy-efficiency plan that includes annual investments in electric energy-efficiency programs of approximately $120 million per year through 2025, which reflects the increased level of annual investments allowed under the IETL. The ICC has the ability to reduce the amount of electric energy-efficiency savings goals in future plan program years if there are insufficient cost-effective programs available, which could reduce the investments in electric energy-efficiency programs. The electric energy-efficiency program investments and the return on those investments are collected from customers through a rider and are not recovered through the electric distribution service performance-based formula ratemaking framework. Illinois Senate Bill 3866 In May 2022, Illinois Senate Bill 3866 was enacted and became effective. This legislation makes certain amendments to the IETL, including amendments to increase the level of funding for the Energy Transition Assistance Fund. As a result of this legislation, Ameren Illinois expects to collect up to $50 million annually related to this fund, beginning in January 2023. Funds collected by Ameren Illinois will be remitted in the month following collection to an Illinois state agency, with no impact to results of operations. RTO Cost Benefit Study In July 2022, an Illinois law prohibiting the state’s oversight of certain electric utilities’ choice of RTO membership ceased to be effective. Given the change in law and the high prices resulting from MISO’s 2022 capacity auction, the ICC issued an order requiring Ameren Illinois to perform a cost benefit study of continued participation in the MISO compared to participation in PJM Interconnection LLC, another RTO. The cost benefit study will examine the impacts of participation in each RTO, including reliability, resiliency, affordability, and environmental impacts, among other things, for a period of five QIP Reconciliation Hearing In March 2020, Ameren Illinois filed its annual request with the ICC for a reconciliation hearing to determine the accuracy and prudence of natural gas capital investments recovered under the QIP rider during 2019. In August 2021, the Illinois Attorney General’s office challenged the recovery of capital investments that were made during 2019, alleging that the ICC should disallow approximately $70 million in natural gas capital investments as improper and imprudent, providing a potential over-recovery of approximately $3 million in 2019. In August and December 2021, the ICC staff filed testimony that supports the prudence and reasonableness of the capital investments made during 2019. Ameren Illinois’ 2019 QIP rate recovery request under review by the ICC is within the rate increase limitations allowed by law. The ICC is under no deadline to issue an order in this proceeding. Federal Transmission Formula Rate Revisions In February 2020, the MISO, on behalf of Ameren Missouri, Ameren Illinois, and ATXI, filed requests with the FERC to revise each company’s transmission formula rate calculations with respect to the calculation used for materials and supplies inventories included in rate base. In May 2020, the FERC issued orders approving the revisions prospectively. In addition, the FERC declined to order refunds for earlier periods, as requested by intervenors in Ameren Illinois’ filing, but directed its audit staff to review historical rate recovery in connection with an ongoing FERC audit. Separately, in March 2021, the FERC issued an order related to an intervenor challenge to Ameren Illinois’ 2020 transmission formula rate update. As a result of this order, in March 2021, Ameren Illinois recorded a regulatory liability of $9 million, largely as a reduction of electric operating revenues, to reflect expected refunds, including interest, primarily related to the historical rate recovery of materials and supplies inventories included in rate base. The refund amount was reflected in rates as of January 2022 and will be refunded to customers by the end of 2022. Ameren Missouri, Ameren Illinois, and ATXI filed appeals of the FERC’s May 2020 and March 2021 orders, and related FERC orders denying requests for rehearing, to the United States Court of Appeals for the District of Columbia Circuit. In January 2022, the appeals were consolidated by the court. The court is under no deadline to address the appeal. Regardless of the outcome of the appeal, the impact of the May 2020 and March 2021 orders is not expected to be material to Ameren’s, Ameren Missouri’s, or Ameren Illinois’ results of operations, financial position, or liquidity. FERC Complaint Cases Since November 2013, the allowed base ROE for FERC-regulated transmission rate base under the MISO tariff has been subject to customer complaint cases and has been changed by various FERC orders. In May 2020, the FERC issued an order, which set the allowed base ROE to 10.02%, and required refunds, with interest, for the periods November 2013 to February 2015 and from late September 2016 forward. In June 2020, various parties filed requests for rehearing with the FERC, challenging the new ROE methodology established by the May 2020 order. In July 2020, the FERC denied the rehearing requests without addressing the issues raised, and indicated it will address the requests for rehearing in a future order. Also in July 2020, Ameren Missouri, Ameren Illinois, and ATXI filed an appeal of the May 2020 order to the United States Court of Appeals for the District of Columbia Circuit, challenging the refunds required for the period from September 2016 to May 2020. The court is under no deadline to address the appeal. Ameren and Ameren Illinois have paid the refunds, including interest, associated with the allowed base ROE set by the May 2020 order.

Short-Term Debt And Liquidity

Short-Term Debt And Liquidity	6 Months Ended
	Jun. 30, 2022
Debt Disclosure [Abstract]
SHORT-TERM DEBT AND LIQUIDITY	SHORT-TERM DEBT AND LIQUIDITY The liquidity needs of the Ameren Companies are typically supported through the use of available cash, drawings under committed credit agreements, commercial paper issuances, and, in the case of Ameren Missouri and Ameren Illinois, short-term affiliate borrowings. See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, in the Form 10-K for a description of our indebtedness provisions and other covenants as well as a description of money pool arrangements. Short-term Borrowings The Missouri Credit Agreement and the Illinois Credit Agreement are available to support issuances under Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper programs, respectively, subject to borrowing sublimits, and the issuance of letters of credit. As of June 30, 2022, based on commercial paper outstanding and letters of credit issued under the Credit Agreements, along with cash and cash equivalents, the net liquidity available to Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively, was $1.3 billion. The Ameren Companies were in compliance with the covenants in their Credit Agreements as of June 30, 2022. As of June 30, 2022, the ratios of consolidated indebtedness to consolidated total capitalization, calculated in accordance with the provisions of the Credit Agreements, were 59%, 51%, and 44% for Ameren, Ameren Missouri, and Ameren Illinois, respectively. The following table presents commercial paper outstanding, net of issuance discounts, as of June 30, 2022, and December 31, 2021. There were no borrowings outstanding under the Credit Agreements as of June 30, 2022, or December 31, 2021. June 30, 2022 December 31, 2021 Ameren (parent) $ 595 $ 277 Ameren Missouri 285 165 Ameren Illinois 141 103 Ameren consolidated $ 1,021 $ 545 The following table summarizes the activity and relevant interest rates for Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper issuances and borrowings under the Credit Agreements in the aggregate for the six months ended June 30, 2022 and 2021: Ameren Ameren Ameren Ameren 2022 Average daily amount outstanding $ 374 $ 271 $ 57 $ 702 Weighted-average interest rate 0.87 % 0.65 % 0.47 % 0.75 % Peak amount outstanding during period (a) $ 595 $ 539 $ 142 $ 1,101 Peak interest rate 2.05 % 2.05 % 2.05 % 2.05 % 2021 Average daily amount outstanding $ 388 $ 183 $ 211 $ 782 Weighted-average interest rate 0.24 % 0.22 % 0.22 % 0.23 % Peak amount outstanding during period (a) $ 650 $ 546 $ 485 $ 1,134 Peak interest rate 0.33 % 0.25 % 0.25 % 0.33 % (a) The timing of peak outstanding commercial paper issuances and borrowings under the Credit Agreements varies by company. Therefore, the sum of individual company peak amounts may not equal the Ameren consolidated peak for the period. Money Pools Ameren has money pool agreements with and among its subsidiaries to coordinate and provide for certain short-term cash and working capital requirements. The average interest rate for borrowings under the utility money pool for the three and six months ended June 30, 2022, was 0.98% and 0.69%, respectively (2021 – 0.22% and 0.22%, respectively). See Note 8 – Related-party Transactions for the amount of interest income and expense from the utility money pool arrangements recorded by Ameren Missouri and Ameren Illinois for the three and six months ended June 30, 2022 and 2021.

Long-Term Debt And Equity Finan

Long-Term Debt And Equity Financings	6 Months Ended
	Jun. 30, 2022
Long-Term Debt And Equity Financings [Abstract]
LONG-TERM DEBT AND EQUITY FINANCINGS	LONG-TERM DEBT AND EQUITY FINANCINGS Ameren For the three and six months ended June 30, 2022, Ameren issued a total of 0.2 million and 0.3 million shares of common stock, respectively, under its DRPlus and 401(k) plan, and received proceeds of $4 million and $17 million, respectively, and had a receivable of $8 million as of June 30, 2022. In addition, in the first quarter of 2022, Ameren issued 0.4 million shares of common stock valued at $31 million upon the settlement of stock-based compensation awards. In May 2021, Ameren entered into an equity distribution sales agreement pursuant to which Ameren may offer and sell from time to time up to $750 million of its common stock through an ATM program, which includes the ability to enter into forward sales agreements. There were no shares issued under the ATM program for the three and six months ended June 30, 2022. As of June 30, 2022, Ameren had approximately $90 million of common stock available under the ATM program, which takes into account the forward sale agreements in effect as of June 30, 2022, discussed below. Ameren has entered into multiple forward sale agreements, including the July 2022 forward sale agreement discussed below, under the ATM program with various counterparties relating to 5.8 million shares of common stock. Ameren expects to settle approximately $300 million of the forward sale agreements by December 31, 2022. Related to the forward sale agreements outstanding as of June 30, 2022, these agreements can be settled at Ameren’s discretion on or prior to dates ranging from May 3, 2023 to February 22, 2024. On a settlement date or dates, if Ameren elects to physically settle the forward sale agreement, Ameren will issue shares of common stock to the counterparties at the then-applicable forward sale price. The initial forward sale price for the agreements ranged from $86.35 to $94.80 with an average initial forward sale price of $89.78. Each initial forward sale price is subject to adjustment based on a floating interest rate factor equal to the overnight bank funding rate less a spread of 75 basis points, and will be subject to decrease on certain dates specified in the forward sale agreements by specified amounts related to expected dividends on shares of the common stock during the term of the forward sale agreements. If the overnight bank funding rate is less than the spread on any day, the interest rate factor will result in a reduction of the forward sale price. The forward sale agreements will be physically settled unless Ameren elects to settle in cash or to net share settle. At June 30, 2022, Ameren could have settled the forward sale agreements with physical delivery of 5.6 million shares of common stock to the respective counterparties in exchange for cash of $500 million. Alternatively, the forward sale agreements could have also been settled at June 30, 2022, with delivery of approximately $8 million of cash or approximately 0.1 million shares of common stock to the counterparties. In connection to the forward sale agreements, the various counterparties, or their affiliates, borrowed from third parties and sold 5.6 million shares of common stock. The gross sales price of these shares totaled $510 million. In connection with such sales, the counterparties were deemed to have received commissions of $5 million. Ameren has not received any proceeds from such sales of borrowed shares. The forward sale agreements have been classified as equity transactions. In July 2022, Ameren entered into a forward sale agreement under the ATM program relating to 0.2 million shares of common stock. The July 2022 forward sale agreement can be settled at Ameren’s discretion on or prior to March 8, 2024. The initial forward sale price was $90.77 for the July 2022 forward sale agreement. Ameren Missouri In April 2022, Ameren Missouri issued $525 million of 3.90% first mortgage bonds due April 2052, with interest payable semiannually on April 1 and October 1 of each year, beginning October 1, 2022. Ameren Missouri received net proceeds of $519 million, which were used to repay short-term debt and for near-term capital expenditures. Ameren Missouri intends to allocate an amount equal to the net proceeds to sustainability projects meeting certain eligibility criteria. ATXI In November 2021, pursuant to a note purchase agreement, ATXI agreed to issue $95 million of its 2.96% senior unsecured notes due 2052, with interest payable semiannually on February 25 and August 25 of each year, beginning February 25, 2023, through a private placement offering exempt from registration under the Securities Act of 1933, as amended. ATXI expects to issue the notes and receive net proceeds of $95 million in August 2022, which will be used to refinance the remaining portion of an intercompany long-term note with Ameren (parent), repay a $50 million principal payment of its 3.43% senior unsecured notes, and to repay short-term debt. Indenture Provisions and Other Covenants See Note 5 – Long-term Debt and Equity Financings under Part II, Item 8, in the Form 10-K for a description of our indenture provisions and other covenants, as well as restrictions on the payment of dividends. At June 30, 2022, the Ameren Companies were in compliance with the provisions and covenants contained in their indentures and articles of incorporation, as applicable, and ATXI was in compliance with the provisions and covenants contained in its note purchase agreements. Off-balance-sheet Arrangements At June 30, 2022, none of the Ameren Companies had any significant off-balance-sheet financing arrangements, other than variable interest entities and the multiple forward sale agreements under the ATM program relating to common stock. See Note 1 – Summary of Significant Accounting Policies for further detail concerning variable interest entities.

Other Income, Net

Other Income, Net	6 Months Ended
	Jun. 30, 2022
Other Nonoperating Income (Expense) [Abstract]
OTHER INCOME, NET	OTHER INCOME, NET The following table presents the components of “Other Income, Net” in the Ameren Companies’ statements of income for the three and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Ameren: Allowance for equity funds used during construction $ 11 $ 9 $ 19 $ 16 Interest income on industrial development revenue bonds 6 6 12 12 Non-service cost components of net periodic benefit income (a) 47 34 93 68 Miscellaneous income 6 7 13 12 Donations (2) (1) (4) (4) Miscellaneous expense (6) (6) (11) (9) Total Other Income, Net $ 62 $ 49 $ 122 $ 95 Ameren Missouri: Allowance for equity funds used during construction $ 6 $ 6 $ 10 $ 10 Interest income on industrial development revenue bonds 6 6 12 12 Non-service cost components of net periodic benefit income (a) 14 14 28 28 Miscellaneous income 1 — 3 1 Donations (1) (1) (2) (1) Miscellaneous expense (2) (1) (4) (3) Total Other Income, Net $ 24 $ 24 $ 47 $ 47 Ameren Illinois: Allowance for equity funds used during construction $ 5 $ 3 $ 9 $ 6 Non-service cost components of net periodic benefit income 21 14 42 28 Miscellaneous income 3 3 5 4 Donations (1) — (2) (3) Miscellaneous expense (3) (4) (5) (5) Total Other Income, Net $ 25 $ 16 $ 49 $ 30 (a) For the three and six months ended June 30, 2022, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $5 million and $11 million, respectively, due to a regulatory tracking mechanism for the difference between the level of such costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. The deferral was $(3) million for both the three and six months ended June 30, 2021. See Note 11– Retirement Benefits for additional information.

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
	Jun. 30, 2022
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE FINANCIAL INSTRUMENTS	DERIVATIVE FINANCIAL INSTRUMENTS We use derivatives to manage the risk of changes in market prices for natural gas, power, and uranium, as well as the risk of changes in rail transportation surcharges through fuel oil hedges. Such price fluctuations may cause the following: • an unrealized appreciation or depreciation of our contracted commitments to purchase or sell when purchase or sale prices under the commitments are compared with current commodity prices; • market values of natural gas and uranium inventories that differ from the cost of those commodities in inventory; • actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays; and • actual off-system sales revenues that differ from anticipated revenues. The derivatives that we use to hedge these risks are governed by our risk management policies for forward contracts, futures, options, and swaps. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The goal of the hedging program is generally to mitigate financial risks while ensuring that sufficient volumes are available to meet our requirements. Contracts we enter into as part of our risk management program may be settled financially, settled by physical delivery, or net settled with the counterparty. All contracts considered to be derivative instruments are required to be recorded on the balance sheet at their fair values, unless the NPNS exception applies. Many of our physical contracts, such as our purchased power contracts, qualify for the NPNS exception to derivative accounting rules. The revenue or expense on NPNS contracts is recognized at the contract price upon physical delivery. The following disclosures exclude NPNS contracts and other non-derivative commodity contracts that are accounted for under the accrual method of accounting. If we determine that a contract meets the definition of a derivative and is not eligible for the NPNS exception, we review the contract to determine whether the resulting gains or losses qualify for regulatory deferral. Derivative contracts that qualify for regulatory deferral are recorded at fair value, with changes in fair value recorded as regulatory assets or liabilities in the period in which the change occurs. We believe derivative losses and gains deferred as regulatory assets and liabilities are probable of recovery, or refund, through future rates charged to customers. Regulatory assets and liabilities are amortized to operating income as related losses and gains are reflected in rates charged to customers. Therefore, gains and losses on these derivatives have no effect on operating income. As of June 30, 2022, and December 31, 2021, all contracts that met the definition of a derivative and were not eligible for the NPNS exception received regulatory deferral. Cash flows for all derivative financial instruments are classified in cash flows from operating activities. The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of June 30, 2022, and December 31, 2021. As of June 30, 2022, these contracts extended through October 2024, October 2027, May 2032 and March 2024 for fuel oils, natural gas, power and uranium, respectively: Quantity (in millions) June 30, 2022 December 31, 2021 Commodity Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren Fuel oils (in gallons) 21 — 21 30 — 30 Natural gas (in mmbtu) 44 152 196 35 144 179 Power (in MWhs) 3 6 9 6 6 12 Uranium (pounds in thousands) 496 — 496 586 — 586 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, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Balance Sheet Location Ameren Ameren Ameren Ameren Ameren Ameren Fuel oils Mark-to-market derivative assets $ 22 $ — $ 22 $ 8 $ — $ 8 Other assets 8 — 8 5 — 5 Natural gas Mark-to-market derivative assets 14 59 73 7 28 35 Other assets 14 27 41 5 13 18 Power Mark-to-market derivative assets 50 9 59 23 — 23 Other assets — 1 1 — — — Uranium Mark-to-market derivative assets 3 — 3 — — — Other assets 1 — 1 1 — 1 Total assets $ 112 $ 96 $ 208 $ 49 $ 41 $ 90 Natural gas Mark-to-market derivative liabilities 4 (a) (a) 2 (a) (a) Other current liabilities — 7 11 — 6 8 Other deferred credits and liabilities 2 4 6 1 2 3 Power Mark-to-market derivative liabilities 141 (a) (a) 50 (a) (a) Other current liabilities — 1 142 — 9 59 Other deferred credits and liabilities 24 53 77 23 108 131 Uranium Mark-to-market derivative liabilities — (a) (a) 1 (a) (a) Other current liabilities — — — — — 1 Total liabilities $ 171 $ 65 $ 236 $ 77 $ 125 $ 202 (a) Balance sheet line item not applicable to registrant. We believe that entering into master netting arrangements or similar agreements mitigates the level of financial loss that could result from default by allowing net settlement of derivative assets and liabilities. These master netting arrangements allow the counterparties to net settle sale and purchase transactions. Further, collateral requirements are calculated at the master netting arrangement or similar agreement level by counterparty. 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, 2022, and December 31, 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 June 30, 2022 Assets: Ameren Missouri $ 112 $ 36 $ 15 $ 61 Ameren Illinois 96 16 15 65 Ameren $ 208 $ 52 $ 30 $ 126 Liabilities: Ameren Missouri $ 171 $ 36 $ 127 $ 8 Ameren Illinois 65 16 — 49 Ameren $ 236 $ 52 $ 127 $ 57 December 31, 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 “Other current assets” and “Other assets” on the balance sheet. Credit Risk In determining our concentrations of credit risk related to derivative instruments, we review our individual counterparties and categorize each counterparty into groupings according to the primary business in which each engages. As of June 30, 2022, if counterparty groups were to fail completely to perform on contracts, Ameren, Ameren Missouri, and Ameren Illinois’ maximum exposure related to derivative assets, predominantly from financial institutions, was $172 million, $83 million, and $89 million, respectively. The potential loss on counterparty exposures may be reduced or eliminated by the application of master netting arrangements or similar agreements and collateral held. As of June 30, 2022, the potential loss after consideration of the application of master netting arrangements or similar agreements and collateral held for Ameren, Ameren Missouri, and Ameren Illinois was $108 million, $42 million, and $66 million, respectively. Certain of our derivative instruments contain collateral provisions tied to the Ameren Companies’ credit ratings. If our credit ratings were downgraded below investment grade, or if a counterparty with reasonable grounds for uncertainty regarding our ability to satisfy an obligation requested adequate assurance of performance, additional collateral postings might be required. The additional collateral required is the net liability position allowed under master netting arrangements or similar agreements, assuming (1) the credit risk-related contingent features underlying these arrangements were triggered and (2) those counterparties with rights to do so requested collateral. The following table presents, as of June 30, 2022, 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: Aggregate Fair Value of Derivative Liabilities (a) Cash Potential Aggregate Amount of Additional Collateral Required (b) Ameren Missouri $ 76 $ 29 $ 12 Ameren Illinois 12 — 4 Ameren $ 88 $ 29 $ 16 (a) Before consideration of master netting arrangements or similar agreements. (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.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value Disclosures	FAIR VALUE MEASUREMENTS Fair value is defined as the price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Fair value measurements are classified in three levels based on the fair value hierarchy as defined by GAAP. See Note 8 – Fair Value Measurements under Part II, Item 8, of the Form 10-K for information related to hierarchy levels and valuation techniques. We consider nonperformance risk in our valuation of derivative instruments by analyzing our own credit standing and the credit standing of our counterparties, and by considering any credit enhancements (e.g., collateral). Included in our valuation, and based on current market conditions, is a valuation adjustment for counterparty default derived from market data such as the price of credit default swaps, bond yields, and credit ratings. No material gains or losses related to valuation adjustments for counterparty default risk were recorded at Ameren, Ameren Missouri, or Ameren Illinois in the three and six months ended June 30, 2022 or 2021. At June 30, 2022, and December 31, 2021, the counterparty default risk valuation adjustment related to derivative contracts was immaterial for Ameren, Ameren Missouri, and Ameren Illinois. 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 June 30, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Ameren Missouri Derivative assets – commodity contracts: Fuel oils $ 27 $ — $ 3 $ 30 $ 13 $ — $ — $ 13 Natural gas 1 27 — 28 — 12 — 12 Power 21 — 29 50 10 — 13 23 Uranium — — 4 4 — — 1 1 Total derivative assets – commodity contracts $ 49 $ 27 $ 36 $ 112 $ 23 $ 12 $ 14 $ 49 Nuclear decommissioning trust fund: Equity securities: U.S. large capitalization $ 602 $ — $ — $ 602 $ 824 $ — $ — $ 824 Debt securities: U.S. Treasury and agency securities — 173 — 173 — 141 — 141 Corporate bonds — 121 — 121 — 131 — 131 Other — 54 — 54 — 56 — 56 Total nuclear decommissioning trust fund $ 602 $ 348 $ — $ 950 (a) $ 824 $ 328 $ — $ 1,152 (a) Total Ameren Missouri $ 651 $ 375 $ 36 $ 1,062 $ 847 $ 340 $ 14 $ 1,201 Ameren Illinois Derivative assets – commodity contracts: Natural gas $ 5 $ 71 $ 10 $ 86 $ 1 $ 33 $ 7 $ 41 Power — — 10 10 — — — — Total Ameren Illinois $ 5 $ 71 $ 20 $ 96 $ 1 $ 33 $ 7 $ 41 Ameren Derivative assets – commodity contracts (b) $ 54 $ 98 $ 56 $ 208 $ 24 $ 45 $ 21 $ 90 Nuclear decommissioning trust fund (c) 602 348 — 950 (a) 824 328 — 1,152 (a) Total Ameren $ 656 $ 446 $ 56 $ 1,158 $ 848 $ 373 $ 21 $ 1,242 Liabilities: Ameren Missouri Derivative liabilities – commodity contracts: Natural gas $ — $ 4 $ 2 $ 6 $ — $ 2 $ 1 $ 3 Power 100 — 65 165 45 — 28 73 Uranium — — — — — — 1 1 Total Ameren Missouri $ 100 $ 4 $ 67 $ 171 $ 45 $ 2 $ 30 $ 77 June 30, 2022 December 31, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Ameren Illinois Derivative liabilities – commodity contracts: Natural gas $ — $ 6 $ 5 $ 11 $ — $ 5 $ 3 $ 8 Power — — 54 54 — — 117 117 Total Ameren Illinois $ — $ 6 $ 59 $ 65 $ — $ 5 $ 120 $ 125 Ameren Derivative liabilities – commodity contracts (b) $ 100 $ 10 $ 126 $ 236 $ 45 $ 7 $ 150 $ 202 (a) Balance exclude s $7 million of cash and cash equivalents, receivables, payables, and accrued income, net, for both June 30, 2022, and December 31, 2021. (b) See the Ameren Missouri and Ameren Illinois sections of the table for a breakout of the fair value of Ameren’s derivative assets and liabilities by type of commodity. (c) See the Ameren Missouri section of the table for a breakout of the fair value of Ameren’s nuclear decommissioning trust fund by investment type. Level 3 fuel oils, natural gas, and uranium derivative contract assets and liabilities measured at fair value on a recurring basis were immaterial for all periods presented. The following table presents the fair value reconciliation of Level 3 power derivative contract assets and liabilities measured at fair value on a recurring basis for the three and six months ended June 30, 2022 and 2021: 2022 2021 Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren For the three months ended June 30: Beginning balance at April 1 $ (53) $ (74) $ (127) $ (3) $ (185) $ (188) Realized and unrealized gains/(losses) included in regulatory assets/liabilities (5) 32 27 (1) 15 14 Settlements 22 (2) 20 (1) 4 3 Ending balance at June 30 $ (36) $ (44) $ (80) $ (5) $ (166) $ (171) Change in unrealized gains/(losses) related to assets/liabilities held at June 30 $ 2 $ 30 $ 32 $ (2) $ 15 $ 13 For the six months ended June 30: Beginning balance at January 1 $ (15) $ (117) $ (132) $ 2 $ (198) $ (196) Realized and unrealized gains/(losses) included in regulatory assets/liabilities (45) 74 29 (6) 24 18 Settlements 24 (1) 23 (1) 8 7 Ending balance at June 30 $ (36) $ (44) $ (80) $ (5) $ (166) $ (171) Change in unrealized gains/(losses) related to assets/liabilities held at June 30 $ (36) $ 72 $ 36 $ (3) $ 24 $ 21 All gains or losses related to our Level 3 derivative commodity contracts are expected to be recovered or returned through customer rates; therefore, there is no impact to either net income or other comprehensive income resulting from changes in the fair value of these instruments. The following table describes the valuation techniques and significant unobservable inputs utilized for the fair value of our Level 3 power derivative contract assets and liabilities as of June 30, 2022, and December 31, 2021: Fair Value Weighted Average (b) Commodity Assets Liabilities Valuation Technique(s) Unobservable Input (a) Range 2022 Power (c) $ 39 $ (119) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 36 – 122 65 Nodal basis ($/MWh) (17) – 3 (6) Trend rate (%) 0 – 3 2 2021 Power (d) $ 13 $ (145) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 32 – 55 40 Nodal basis ($/MWh) (14) – 0 (2) Trend rate (%) (e) 0 (a) Generally, significant increases (decreases) in these inputs in isolation would result in a significantly higher (lower) fair value measurement. (b) Unobservable inputs were weighted by relative fair value. (c) Valuations through 2031 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2031 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials. (d) Valuations through 2029 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2029 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials. (e) No meaningful range around weighted average. The following table sets forth the carrying amount and, by level within the fair value hierarchy, the fair value of financial assets and liabilities disclosed, but not recorded, at fair value as of June 30, 2022, and December 31, 2021: Carrying Fair Value Level 1 Level 2 Level 3 Total June 30, 2022 Ameren: Cash, cash equivalents, and restricted cash $ 161 $ 161 $ — $ — $ 161 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 1,021 — 1,021 — 1,021 Long-term debt (including current portion) (a) 13,590 (b) — 12,016 500 (c) 12,516 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 7 $ 7 $ — $ — $ 7 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 285 — 285 — 285 Long-term debt (including current portion) (a) 6,139 (b) — 5,641 — 5,641 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 146 $ 146 $ — $ — $ 146 Short-term debt 141 — 141 — 141 Long-term debt (including current portion) 4,394 (b) — 4,037 — 4,037 December 31, 2021 Ameren: Cash, cash equivalents, and restricted cash $ 155 $ 155 $ — $ — $ 155 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 545 — 545 — 545 Long-term debt (including current portion) (a) 13,067 (b) — 13,930 591 (c) 14,521 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 8 $ 8 $ — $ — $ 8 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 165 — 165 — 165 Long-term debt (including current portion) (a) 5,619 (b) — 6,321 — 6,321 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 133 $ 133 $ — $ — $ 133 Short-term debt 103 — 103 — 103 Long-term debt (including current portion) 4,392 (b) — 4,971 — 4,971 (a) Ameren and Ameren Missouri have investments in industrial development revenue bonds, classified as held-to-maturity and recorded in “Other Assets,” that are equal to the finance obligations for the Peno Creek and Audrain CT energy centers. As of June 30, 2022, and December 31, 2021, the carrying amount of both the investments in industrial development revenue bonds and the finance obligations approximated fair value. (b) Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $97 million, $43 million, and $37 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of June 30, 2022. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $94 million, $38 million, and $39 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2021. (c) The Level 3 fair value amount consists of ATXI’s senior unsecured notes.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2022
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED-PARTY TRANSACTIONS In the ordinary course of business, Ameren Missouri and Ameren Illinois have engaged in, and may in the future engage in, affiliate transactions. These transactions primarily consist of natural gas and power purchases and sales, services received or rendered, and borrowings and lendings. Transactions between Ameren’s subsidiaries are reported as affiliate transactions on their individual financial statements, but those transactions are eliminated in consolidation for Ameren’s consolidated financial statements. For a discussion of material related-party agreements and money pool arrangements, see Note 13 – Related-party Transactions and Note 4 – Short-term Debt and Liquidity under Part II, Item 8, of the Form 10-K. Support Services Agreements Ameren Missouri and Ameren Illinois had long-term receivables included in “Other assets” from Ameren Services of $80 million and $83 million, respectively, as of June 30, 2022, and $77 million and $80 million, respectively, as of December 31, 2021, related to Ameren Services’ allocated portion of Ameren’s pension and postretirement benefit plans. Tax Allocation Agreement See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for a discussion of the tax allocation agreement. The following table presents the affiliate balances related to income taxes for Ameren Missouri and Ameren Illinois as of June 30, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Ameren Missouri Ameren Illinois Ameren Missouri Ameren Illinois Income taxes payable to parent (a) $ — $ 82 $ — $ 8 Income taxes receivable from parent (b) 45 — 27 18 (a) Included in “Accounts payable – affiliates” on the balance sheet. (b) Included in “Accounts receivable – affiliates” on the balance sheet. Effects of Related-party Transactions on the Statement of Income The following table presents the impact on Ameren Missouri and Ameren Illinois of related-party transactions for the three and six months ended June 30, 2022 and 2021: Three Months Six Months Agreement Income Statement Ameren Ameren Ameren Ameren Ameren Missouri power supply Operating Revenues 2022 $ 1 $ (a) $ 5 $ (a) agreements with Ameren Illinois 2021 3 (a) 5 (a) Ameren Missouri and Ameren Illinois Operating Revenues 2022 $ 6 $ (b) $ 12 $ (b) rent and facility services 2021 7 (b) 14 (b) Ameren Missouri and Ameren Illinois miscellaneous Operating Revenues 2022 $ (b) $ (b) $ (b) $ 1 support services and other services provided to ATXI 2021 (b) 2 (b) 2 Total Operating Revenues 2022 $ 7 $ (b) $ 17 $ 1 2021 10 2 19 2 Ameren Illinois power supply Purchased Power 2022 $ (a) $ 1 $ (a) $ 5 agreements with Ameren Missouri 2021 (a) 3 (a) 5 Ameren Missouri and Ameren Illinois Purchased Power 2022 $ (b) $ (b) $ (b) $ (b) transmission services from ATXI 2021 1 1 2 1 Total Purchased Power 2022 $ (b) $ 1 $ (b) $ 5 2021 1 4 2 6 Ameren Missouri and Ameren Illinois Other Operations and Maintenance 2022 $ (b) $ (b) $ (b) $ 1 rent and facility services 2021 (b) 1 (b) 2 Ameren Services support services Other Operations and Maintenance 2022 $ 33 $ 32 $ 71 $ 67 agreement 2021 34 31 69 64 Total Other Operations and 2022 $ 33 $ 32 $ 71 $ 68 Maintenance 2021 34 32 69 66 Money pool borrowings (advances) (Interest Charges)/Other Income, Net 2022 $ (b) $ (b) $ (b) $ (b) 2021 (b) (b) (b) (b) (a) Not applicable. (b) Amount less than $1 million.

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES We are involved in legal, tax, and regulatory proceedings before various courts, regulatory commissions, authorities, and governmental agencies with respect to matters that arise in the ordinary course of business, some of which involve substantial amounts of money. We believe that the final disposition of these proceedings, except as otherwise disclosed in the notes to our financial statements in this report and in the Form 10-K, will not have a material adverse effect on our results of operations, financial position, or liquidity. Reference is made to Note 1 – Summary of Significant Accounting Policies, Note 2 – Rate and Regulatory Matters, Note 9 – Callaway Energy Center, Note 13 – Related-party Transactions, and Note 14 – Commitments and Contingencies under Part II, Item 8, of the Form 10-K. See also Note 1 – Summary of Significant Accounting Policies, Note 2 – Rate and Regulatory Matters, Note 8 – Related-party Transactions, and Note 10 – Callaway Energy Center of this report. Environmental Matters Our electric generation, transmission, and distribution and natural gas distribution and storage operations must comply with a variety of statutes and regulations relating to the protection of the environment and human health and safety including permitting programs implemented via federal, state, and local authorities. Such environmental laws address air emissions; discharges to water bodies; the storage, handling and disposal of hazardous substances and waste materials; siting and land use requirements; and potential ecological impacts. Complex and lengthy processes are required to obtain and renew approvals, permits, and licenses for new, existing, or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials require release prevention plans and emergency response procedures. We employ dedicated personnel knowledgeable in environmental matters to oversee our business activities’ compliance with regulatory requirements. Environmental regulations have a significant impact on the electric utility industry and compliance with these regulations could be costly for Ameren Missouri, which operates coal-fired power plants. Regulations under the Clean Air Act that apply to the electric utility industry include the NSPS, the CSAPR, the MATS, and the National Ambient Air Quality Standards, which are subject to periodic review for certain pollutants. Collectively, these regulations cover a variety of pollutants, such as SO 2 , particulate matter, NOx, mercury, toxic metals and acid gases, and CO 2 emissions from new power plants. Regulations implementing the Clean Water Act govern both intake and discharges of water, and may require evaluation of the ecological and biological impact of our operations and could require modifications to water intake structures or more stringent limitations on wastewater discharges. Depending upon the scope of modifications ultimately required by state regulators, capital expenditures associated with these modifications could be significant. The management and disposal of coal ash is regulated under the Resource Conservation and Recovery Act and the CCR Rule, which require the closure of certain surface impoundments at Ameren Missouri’s coal-fired energy centers. The individual or combined effects of existing and new environmental regulations could result in significant capital expenditures, increased operating costs, or the closure or alteration of operations at some of Ameren Missouri’s energy centers. Ameren and Ameren Missouri expect that such compliance costs would be recoverable through rates, subject to MoPSC prudence review, but the timing of costs and their recovery could be subject to regulatory lag. Additionally, Ameren Missouri’s wind generation facilities may be subject to operating restrictions to limit the impact on protected species. Nighttime operating restrictions may be required during the critical biological season, which typically occurs from April through October. Seasonal nighttime curtailment began at the High Prairie Renewable Energy Center at the end of March 2022, but the extent and duration of the curtailment is unknown at this time as assessment of mitigation technologies is ongoing. Ameren Missouri does not anticipate these operating curtailments to result in significant impacts on its results of operations, financial position, or liquidity. Ameren and Ameren Missouri estimate that they will need to make capital expenditures of $125 million to $175 million from 2022 through 2026 in order to comply with existing environmental regulations. Additional environmental controls beyond 2026 could be required. This estimate of capital expenditures includes ash pond closure and corrective action measures required by the CCR Rule and the effluent limitation guidelines applicable to steam electric generating units, and potential modifications to cooling water intake structures at existing power plants under Clean Water Act rules, all of which are discussed below. In addition to planned retirements of fossil fuel-fired energy centers as set forth in the 2022 Change to the 2020 IRP filed with the MoPSC in June 2022 and as noted in the NSR and Clean Air Act litigation and Illinois emissions standards discussed below, Ameren Missouri’s current plan for compliance with existing air emission regulations includes burning low-sulfur coal and installing new or optimizing existing air pollution control equipment. The actual amount of capital expenditures required to comply with existing environmental regulations may vary substantially from the above estimates because of uncertainty as to future permitting requirements made by state regulators and the EPA, potential revisions to regulatory obligations, and the cost of potential compliance strategies, among other things. The following sections describe the more significant environmental laws and rules and environmental enforcement and remediation matters that affect or could affect our operations. The EPA has initiated an administrative review of several regulations and proposed amendments to regulations and guidelines, including the CSAPR, which could ultimately result in the revision of all or part of such rules. Clean Air Act Federal and state laws, including CSAPR, regulate emissions of SO 2 and NO x through the reduction of emissions at their source and the use and retirement of emission allowances. CSAPR is implemented through a series of phases, and the second phase became effective in 2017. In April 2022, the EPA proposed plans for additional emission reductions from power plants in Missouri, Illinois, and other states through revisions to the CSAPR; and additional emission reduction requirements may apply in subsequent years. The EPA expects to issue a final rule in March 2023. Ameren Missouri complies with current CSAPR requirements by minimizing emissions through the use of low-sulfur coal, operation of two scrubbers at its Sioux Energy Center, and optimization of other existing air pollution control equipment. Ameren Missouri could incur additional costs to lower its emissions at one or more of its energy centers to comply with additional CSAPR requirements in future years. These additional costs for compliance are expected to be recovered from customers through the FAC or higher base rates. CO 2 Emissions Standards In June 2022, the United States Supreme Court issued its decision in West Virginia v. EPA . The decision clarifies that there are limits on how the EPA may regulate greenhouse gases absent further direction from the United States Congress. The court concluded that emission caps that would cause generation shifting from fossil-fuel-fired power plants to renewable energy facilities would require specific congressional authorization and that such authorization had not been given under the Clean Air Act. The decision by the United States Supreme Court may affect the EPA’s development of any new regulations to address CO 2 emissions from coal- and natural gas-fired power plants; however, at this time, Ameren Missouri cannot predict the impact of any such regulations or the decision by the United States Supreme Court on the results of operations, financial position, and liquidity of Ameren or Ameren Missouri. NSR and Clean Air Act Litigation In January 2011, the United States Department of Justice, on behalf of the EPA, filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri alleging that in performing projects at its coal-fired Rush Island Energy Center in 2007 and 2010, Ameren Missouri violated provisions of the Clean Air Act and Missouri law. In January 2017, the district court issued a liability ruling against Ameren Missouri and, in September 2019, entered a remedy order that required Ameren Missouri to install a flue gas desulfurization system at the Rush Island Energy Center and a dry sorbent injection system at the Labadie Energy Center. Following an appeal from Ameren Missouri in August 2021, the United States Court of Appeals for the Eighth Circuit affirmed the liability ruling and the district court’s remedy order as it related to the installation of a flue gas desulfurization system at the Rush Island Energy Center, but reversed the order as it related to the installation of a dry sorbent injection system at the Labadie Energy Center. In November 2021, the court of appeals issued an order denying requests for consideration previously sought by both Ameren Missouri and the United States Department of Justice. Based on its assessment of available legal, operational, and regulatory alternatives, Ameren Missouri filed a motion in December 2021, with the district court to modify the remedy order to allow the retirement of the Rush Island Energy Center in advance of its previously expected useful life in lieu of installing a flue gas desulfurization system. In June 2022, Ameren Missouri supplemented its filing with the district court by proposing reduced operations, mostly operating during peak demand times and emergencies until the energy center is retired. The March 31, 2024 compliance date contained in the district court’s September 2019 remedy order remains in effect unless extended by the district court. In July 2022, in response to an Ameren Missouri request for a final, binding reliability assessment, the MISO designated the Rush Island Energy Center as a system support resource and concluded that certain mitigation measures, including transmission upgrades, should occur before the energy center is retired. The transmission upgrade projects have been approved by the MISO, and Ameren Missouri has started design and procurement activities necessary to complete the upgrades and expects to complete the upgrades by late 2025. The FERC will need to approve a system support resource agreement detailing the manner of continued operation of the Rush Island Energy Center, as well as a request from Ameren Missouri for recovery of non-energy costs under the related MISO tariff. The agreement, if approved, would have a term of 12 months. The system support resource designation and the related agreement are subject to renewal and revision. Any difference between revenues and costs under the MISO tariff is expected to be included in the FAC. The district court has the authority to determine the retirement date and operating parameters for the Rush Island Energy Center and is not bound by the MISO determination of the Rush Island Energy Center as a system support resource or the FERC’s approval. While the district court is under no deadline to issue a ruling modifying the remedy order, a decision is expected in the near term. Related to this matter, in February 2022, the MoPSC issued an order directing the MoPSC staff to review the planned accelerated retirement of the Rush Island Energy Center. See Note 2 – Rate and Regulatory Matters for additional information. In connection with the planned accelerated retirement of the Rush Island Energy Center, Ameren Missouri expects to seek approval from the MoPSC to finance the costs associated with the retirement, including the remaining unrecovered net plant balance associated with the facility, through the issuance of securitized utility tariff bonds pursuant to the Missouri securitization statute. As such, Ameren Missouri did not request a change in the depreciation rates related to the Rush Island Energy Center in the electric regulatory rate review filed in August 2022. See Note 2 – Rate and Regulatory Matters for additional information on the August 2022 electric regulatory rate review. As of June 30, 2022, the Rush Island Energy Center had a net plant balance of approximately $0.6 billion included in plant to be abandoned, net, within “Property, Plant, and Equipment, Net” and a rate base of approximately $0.5 billion. See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for additional information regarding plant to be abandoned, net. In addition, Ameren Missouri filed a 2022 Change to the 2020 IRP with the MoPSC in June 2022 to reflect, among other things, the planned acceleration of the retirement of the Rush Island Energy Center from 2039, the retirement year for the facility as reflected in the 2020 IRP and reflected in depreciation rates approved by the December 2021 MoPSC electric rate order. Ameren Missouri is unable to predict the ultimate resolution of this matter; however, such resolution could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. Clean Water Act The EPA’s regulations implementing Section 316(b) of the Clean Water Act require power plant operators to evaluate cooling water intake structures and identify measures for reducing the number of aquatic organisms impinged on a power plant’s cooling water intake screens or entrained through the plant’s cooling water system. All of Ameren Missouri’s coal-fired and nuclear energy centers are subject to the cooling water intake structures rule. Requirements of the rule are implemented by state regulators through the permit renewal process of each power plant’s water discharge permit, which is expected to be completed by 2023 for Ameren Missouri. In 2015, the EPA issued a rule to revise the effluent limitation guidelines applicable to steam electric generating units. These guidelines established national standards for water discharges, prohibit effluent discharges of certain waste streams, and impose more stringent limitations on certain water discharges from power plants. To meet the requirements of the guidelines, Ameren Missouri installed dry ash handling systems and in 2020 completed construction of wastewater treatment facilities at three of its four coal-fired energy centers. The Meramec Energy Center is scheduled to retire in 2022 and, as a result, does not require new wastewater and dry ash handling systems. CCR Management The EPA’s CCR Rule establishes requirements for the management and disposal of CCR from coal-fired power plants and will result in the closure of certain surface impoundments at Ameren Missouri’s energy centers. Ameren Missouri completed the closure of all surface impoundments at its Labadie and Rush Island energy centers in 2021, and has made significant progress by closing several surface impoundments at its Sioux and Meramec energy centers. Ameren Missouri plans to complete the closures of the remaining surface impoundments as required by the CCR Rule in 2023. In January 2022, Ameren Missouri received notice of a proposed determination by the EPA that it has rejected Ameren Missouri’s requests to extend the timeline for operating certain surface impoundments located at the Sioux and Meramec energy centers. Pursuant to the terms of the proposed determination, compliance with the CCR Rule’s requirements for closure of the surface impoundments would be required 135 days after the EPA issues a final determination. In February 2022, Ameren Missouri filed comments with the EPA requesting additional time to construct a CCR Rule-compliant impoundment at the Sioux Energy Center and complete the closure of the surface impoundments at the Meramec Energy Center. The EPA is under no deadline to issue a final determination. If Ameren Missouri was no longer able to use the surface impoundments at the Sioux or Meramec energy centers, Ameren Missouri would not be able to operate the energy centers unless an alternative for handling the CCR material was available. Ameren Missouri will retire the Meramec Energy Center in 2022, and construction of a CCR Rule-compliant surface impoundment at the Sioux Energy Center is expected to be completed by the fall of 2022 to allow for continued operations. Ameren Missouri does not expect that this matter will have a material adverse effect on its results of operations, financial position, or liquidity. Ameren and Ameren Missouri have AROs of $77 million recorded on their respective balance sheets as of June 30, 2022, associated with CCR storage facilities. Ameren Missouri estimates it will need to make capital expenditures of $60 million to $80 million from 2022 through 2026 to implement its CCR management compliance plan, which includes installation of groundwater monitoring equipment and groundwater treatment facilities. Remediation The Ameren Companies are involved in a number of remediation actions to clean up sites impacted by the use or disposal of materials containing hazardous substances. Federal and state laws can require responsible parties to fund remediation regardless of their degree of fault, the legality of original disposal, or the ownership of a disposal site. As of June 30, 2022, Ameren Illinois has remediated the majority of the 44 former MGP sites in Illinois and could substantially conclude remediation efforts at the remaining sites by 2023. The ICC allows Ameren Illinois to recover such remediation and related litigation costs from its electric and natural gas utility customers through environmental cost riders that are subject to annual prudence reviews by the ICC. As of June 30, 2022, Ameren Illinois estimated the remaining obligation related to these former MGP sites at $78 million to $147 million. Ameren and Ameren Illinois recorded a liability of $78 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate. The scope of the remediation activities at these former MGP sites may increase as remediation efforts continue. Considerable uncertainty remains in these estimates because many site-specific factors can influence the actual costs, including unanticipated underground structures, the degree to which groundwater is encountered, regulatory changes, local ordinances, and site accessibility. The actual costs and timing of completion may vary substantially from these estimates. Our operations or those of our predecessor companies involve the use of, disposal of, and, in appropriate circumstances, the cleanup of substances regulated under environmental laws. We are unable to determine whether such historical practices will result in future environmental commitments or will affect our results of operations, financial position, or liquidity. Illinois Emission Standards The IETL established emission standards that became effective in September 2021. Ameren Missouri’s natural gas-fired energy centers in Illinois are subject to limits on emissions, including CO 2 and NOx, equal to their unit-specific average emissions from 2018 through 2020, for any rolling twelve-month period beginning October 1, 2021, through 2029. Further reductions to emissions limits will become effective between 2030 and 2040, resulting in the closure of the Venice Energy Center by 2029. The reductions could also limit the operations of Ameren Missouri’s other four natural gas-fired energy centers located in the state of Illinois, and will result in their closure by 2040. These energy centers are utilized to support peak loads. Subject to conditions in the IETL, these energy centers may be allowed to exceed the emissions limits in order to maintain reliability of electric utility service as necessary. Ameren Missouri filed a 2022 Change to the 2020 IRP with the MoPSC in June 2022 to reflect, among other things, the updated scheduled retirement dates of the natural gas-fired energy centers located in the state of Illinois.

Callaway Energy Center

Callaway Energy Center	6 Months Ended
	Jun. 30, 2022
Nuclear Waste Matters [Abstract]
CALLAWAY ENERGY CENTER	CALLAWAY ENERGY CENTER See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for information regarding spent nuclear fuel recovery, recovery of decommissioning costs, and the nuclear decommissioning trust fund. The fair value of the trust fund for Ameren Missouri’s Callaway Energy Center is reported as “Nuclear decommissioning trust fund” in Ameren’s and Ameren Missouri’s balance sheets. This amount is legally restricted and may be used only to fund the costs of nuclear decommissioning. Changes in the fair value of the trust fund are recorded as an increase or decrease to the nuclear decommissioning trust fund, with an offsetting adjustment to the related regulatory liability. Ameren and Ameren Missouri have recorded an ARO for the Callaway Energy Center decommissioning costs at fair value, which represents the present value of estimated future cash outflows. Annual decommissioning costs of $7 million are included in the costs used to establish electric rates for Ameren Missouri’s customers. Every three years, the MoPSC requires Ameren Missouri to file an updated cost study and funding analysis for decommissioning its Callaway Energy Center. An updated cost study and funding analysis was filed with the MoPSC in November 2020 and reflected within the ARO. In February 2021, the MoPSC approved no change in electric rates for decommissioning costs based on Ameren Missouri’s updated cost study funding analysis. See Note 13 – Supplemental Information for more information on Ameren Missouri’s AROs. Maintenance Outage See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for information regarding a maintenance outage from a non-nuclear operating issue related to the Callaway Energy Center’s generator in late December 2020 and subsequent return to service on August 4, 2021, along with the related insurance claims. In April 2022, Ameren Missouri received $22 million from NEIL related to lost sales insurance claims. Insurance The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at June 30, 2022: Type and Source of Coverage Most Recent Maximum Coverages Maximum Assessments Public liability and nuclear worker liability: American Nuclear Insurers January 1, 2022 $ 450 $ — Pool participation (a) 13,073 (a) 138 (b) $ 13,523 (c) $ 138 Property damage: NEIL and EMANI April 1, 2022 $ 3,200 (d) $ 26 (e) Accidental outage: NEIL April 1, 2022 $ 490 (f) $ 7 (e) (a) Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the program. (b) Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $450 million in the event of an incident at any licensed United States commercial reactor, payable at $21 million per year. (c) Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. This limit is subject to change to account for the effects of inflation and changes in the number of licensed power reactors. (d) NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $2.3 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events. (e) All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL. (f) Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are limited to $328 million. The Price-Anderson Act is a federal law that limits the liability for claims from an incident involving any licensed United States commercial nuclear energy center. The limit is based on the number of licensed reactors. The limit of liability and the maximum potential annual payments are adjusted at least every five years for inflation to reflect changes in the Consumer Price Index. The most recent five-year inflationary adjustment became effective in November 2018. Owners of a nuclear reactor cover this exposure through a combination of private insurance and mandatory participation in a financial protection pool, as established by the Price-Anderson Act. Losses resulting from terrorist attacks on nuclear facilities insured by NEIL are subject to industrywide aggregates, such that terrorist acts against one or more commercial nuclear power plants within a stated time period would be treated as a single event, and the owners of the nuclear power plants would share the limit of liability. NEIL policies have an aggregate limit of $3.2 billion within a 12-month period for radiation events, or $1.8 billion for events not involving radiation contamination, resulting from terrorist attacks. The EMANI policies are not subject to industrywide aggregates in the event of terrorist attacks on nuclear facilities. If losses from a nuclear incident at the Callaway Energy Center exceed the limits of, or are not covered by insurance, or if coverage is unavailable, Ameren Missouri is at risk for any uninsured losses. If a serious nuclear incident were to occur, it could have a material adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, or liquidity.

Retirement Benefits

Retirement Benefits	6 Months Ended
	Jun. 30, 2022
Retirement Benefits [Abstract]
RETIREMENT BENEFITS	RETIREMENT BENEFITS The following table presents the components of the net periodic benefit cost (income) incurred for Ameren’s pension and postretirement benefit plans for the three and six months ended June 30, 2022 and 2021: Pension Benefits Postretirement Benefits Three Months Six Months Three Months Six Months 2022 2021 2022 2021 2022 2021 2022 2021 Service cost (a) $ 31 $ 34 $ 64 $ 67 $ 5 $ 6 $ 10 $ 12 Non-service cost components: Interest cost 41 38 81 76 9 8 17 16 Expected return on plan assets (80) (74) (160) (149) (22) (20) (43) (40) Amortization of: Prior service benefit — — — — (1) (1) (2) (2) Actuarial loss (gain) 6 20 12 37 (5) (2) (9) (3) Total non-service cost components (b) $ (33) $ (16) $ (67) $ (36) $ (19) $ (15) $ (37) $ (29) Net periodic benefit cost (income) (c) $ (2) $ 18 $ (3) $ 31 $ (14) $ (9) $ (27) $ (17) (a) Service cost, net of capitalization, is reflected in “Operating Expenses – Other operations and maintenance” on Ameren’s statement of income. (b) Non-service cost components are reflected in “Other Income, Net” on Ameren’s statement of income. See Note 5 – Other Income, Net, for additional information. (c) Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. Ameren Missouri and Ameren Illinois are responsible for their respective share of Ameren’s pension and other postretirement costs. The following table presents the respective share of net periodic pension and other postretirement benefit costs (income) incurred for the three and six months ended June 30, 2022 and 2021: Pension Benefits Postretirement Benefits Three Months Six Months Three Months Six Months 2022 2021 2022 2021 2022 2021 2022 2021 Ameren Missouri (a) $ (1) $ 9 $ (2) $ 15 $ (4) $ (1) $ (7) $ (2) Ameren Illinois — 9 1 17 (10) (8) (20) (15) Other (1) — (2) (1) — — — — Ameren (a) $ (2) $ 18 $ (3) $ 31 $ (14) $ (9) $ (27) $ (17) (a) Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2022
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three and six months ended June 30, 2022 and 2021: Ameren Ameren Missouri Ameren Illinois 2022 2021 2022 2021 2022 2021 Three Months Federal statutory corporate income tax rate 21 % 21 % 21 % 21 % 21 % 21 % Increases (decreases) from: Amortization of deferred investment tax credit — — (1) (1) — — Amortization of excess deferred taxes (a) (8) (9) (15) (17) (2) (2) Depreciation differences — — — 1 (1) 1 Other 1 — — — — — Renewable and other tax credits (b) (4) (4) (10) (10) — (1) State tax 5 5 3 3 7 7 Effective income tax rate 15 % 13 % (2) % (3) % 25 % 26 % Six Months Federal statutory corporate income tax rate 21 % 21 % 21 % 21 % 21 % 21 % Increases (decreases) from: Amortization of deferred investment tax credit — — (1) (1) — — Amortization of excess deferred taxes (a) (8) (9) (16) (17) (2) (3) Depreciation differences — — — 1 — — Renewable and other tax credits (b) (5) (5) (10) (10) — — State tax 5 5 3 3 7 7 Effective income tax rate 13 % 12 % (3) % (3) % 26 % 25 % (a) Reflects the amortization of amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. Deferred income taxes are revalued when federal or state income tax rates change, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory asset or liability. (b) Includes credits associated with the High Prairie and Atchison renewable energy centers. Ameren Missouri placed the High Prairie Renewable Energy Center in service in December 2020. Additionally, Ameren Missouri placed in service the wind turbines at its Atchison Renewable Energy Center throughout the first half of 2021. The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.

Supplemental Information

Supplemental Information	6 Months Ended
	Jun. 30, 2022
Supplemental Information [Abstract]
Supplemental Information	SUPPLEMENTAL INFORMATION Cash, Cash Equivalents, and 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 at June 30, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Ameren Ameren Ameren Ameren Ameren Ameren “Cash and cash equivalents” $ 7 $ — $ — $ 8 $ — $ — Restricted cash included in “Other current assets” 7 2 4 16 4 6 Restricted cash included in “Other assets” 142 — 142 127 — 127 Restricted cash included in “Nuclear decommissioning trust fund” 5 5 — 4 4 — Total cash, cash equivalents, and restricted cash $ 161 $ 7 $ 146 $ 155 $ 8 $ 133 Restricted cash included in “Other current assets” primarily represents funds held by an irrevocable Voluntary Employee Beneficiary Association (VEBA) trust, which provides health care benefits for active employees. Restricted cash included in “Other assets” on Ameren’s and Ameren Illinois’ balance sheets primarily represents amounts collected under a cost recovery rider restricted for use in the procurement of renewable energy credits and amounts in a trust fund restricted for the use of funding certain asbestos-related claims. Accounts Receivable “Accounts receivable – trade” on Ameren’s and Ameren Illinois’ balance sheets include certain receivables purchased at a discount from alternative retail electric suppliers that elect to participate in the utility consolidated billing program. At June 30, 2022, and December 31, 2021, “Other current liabilities” on Ameren’s and Ameren Illinois’ balance sheets included payables for purchased receivables of $32 million and $27 million, respectively. The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the three and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Ameren: Beginning of period $ 28 $ 47 $ 29 $ 50 Bad debt expense 7 (3) 11 1 Net write-offs (5) (2) (10) (9) End of period $ 30 $ 42 $ 30 $ 42 Ameren Missouri: Beginning of period $ 11 $ 15 $ 13 $ 16 Bad debt expense 2 2 3 3 Net write-offs (1) (1) (4) (3) End of period $ 12 $ 16 $ 12 $ 16 Ameren Illinois: (a) Beginning of period $ 17 $ 32 $ 16 $ 34 Bad debt expense 5 (5) (b) 8 (2) (b) Net write-offs (4) (1) (6) (6) End of period $ 18 $ 26 $ 18 $ 26 (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. (b) In the three and six months ended June 30, 2021, Ameren Illinois’ bad debt expense was reduced as a result of state funding received for customer bill assistance. Supplemental Cash Flow Information Capital expenditures for the six months ended June 30, 2021, at Ameren and Ameren Missouri included wind generation expenditures of $417 million. The following table provides noncash financing and investing activity excluded from the statements of cash flows for the six months ended June 30, 2022 and 2021: June 30, 2022 June 30, 2021 Ameren Ameren Ameren Ameren Ameren Ameren Investing Accrued capital expenditures $ 408 $ 204 $ 193 $ 434 $ 259 $ 174 Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund (211) (211) — 85 85 — Financing Issuance of common stock for stock-based compensation $ 31 $ — $ — $ 33 $ — $ — Issuance of common stock under the DRPlus 8 — — — — — Asset Retirement Obligations The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the six months ended June 30, 2022: Ameren Ameren Ameren Balance at December 31, 2021 $ 760 (a) $ 4 (b) $ 764 (a) Accretion 15 (c) — 15 (c) Change in estimates 2 — 2 Balance at June 30, 2022 $ 777 (a) $ 4 (b) $ 781 (a) (a) Balance included $7 million in “Other current liabilities” on the balance sheet as of both June 30, 2022, and December 31, 2021. (b) Included in “Other deferred credits and liabilities” on the balance sheet. (c) Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities. Stock-based Compensation Ameren’s long-term incentive plan available for eligible employees, the 2014 Omnibus Incentive Compensation Plan (2014 Plan), was replaced prospectively for new grants only by the 2022 Omnibus Incentive Compensation Plan (2022 Plan) effective May 12, 2022. The 2022 Plan provides for a maximum of 8.8 million common shares to be available for grant to eligible employees and directors, and retains many of the features of the 2014 Plan. The 2022 Plan permits the grant of restricted stock, restricted stock units, stock options (incentive stock options and nonqualified stock options), stock appreciation rights, performance awards, cash-based awards and other stock-based awards. In the first quarter of 2022 under the 2014 Plan, Ameren granted 267,849 performance share units with a grant date fair value of $25 million and 122,882 restricted share units with a grant date fair value of $11 million. Awards vest approximately 3 years after the grant date or on a pro-rata basis upon death or eligible retirement. The performance share units vest based on the achievement of certain specified market performance measures (229,566 performance share units) or clean energy transition targets (38,283 performance share units). The exact number of shares issued pursuant to a performance share unit varies from 0% to 200% of the target award, depending on actual company performance relative to the performance goals. For the six months ended June 30, 2022 and 2021, excess tax benefits associated with the settlement of stock-based compensation awards reduced income tax expense by $5 million in both periods. Deferred Compensation At June 30, 2022, and December 31, 2021, the present value of benefits to be paid for deferred compensation obligations was $89 million and $91 million, respectively, which was primarily reflected in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet. Operating Revenues As of June 30, 2022 and 2021, our remaining performance obligations for contracts with a term greater than one year were immaterial. The Ameren Companies elected not to disclose the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied as of the end of the reporting period for contracts with an initial expected term of one year or less. See Note 14 – Segment Information for disaggregated revenue information. Excise Taxes Ameren Missouri and Ameren Illinois collect from their customers excise taxes, including municipal and state excise taxes and gross receipts taxes that are levied on the sale or distribution of natural gas and electricity. 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 and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Ameren Missouri $ 39 $ 35 $ 73 $ 66 Ameren Illinois 28 27 73 66 Ameren $ 67 $ 62 $ 146 $ 132 Earnings per Share 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 and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Weighted-average Common Shares Outstanding – Basic 258.2 256.1 258.0 255.2 Assumed settlement of performance share units and restricted stock units 1.0 1.1 1.1 1.3 Dilutive effect of forward sale agreements 0.2 — 0.1 — Weighted-average Common Shares Outstanding – Diluted (a) 259.4 257.2 259.2 256.5 (a) There was an immaterial number of anti-dilutive securities excluded from the earnings per diluted share calculations for the three and six months ended June 30, 2022. There were no anti-dilutive securities excluded from the earnings per diluted share calculations for the three and six months ended June 30, 2021.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2022
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three and six months ended June 30, 2022 and 2021. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount. For additional information about our segments, see Note 16 – Segment Information under Part II, Item 8, of the Form 10-K. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Other Intersegment Eliminations Ameren Three Months 2022: External revenues $ 912 $ 504 $ 184 $ 126 $ — $ — $ 1,726 Intersegment revenues 7 — — 24 — (31) — Net income (loss) attributable to Ameren common shareholders 100 51 6 63 (a) (13) — 207 Capital expenditures 392 143 69 160 1 (1) 764 Three Months 2021: External revenues $ 799 $ 386 $ 168 $ 119 $ — $ — $ 1,472 Intersegment revenues 10 2 — 17 — (29) — Net income (loss) attributable to Ameren common shareholders 111 41 8 55 (a) (8) — 207 Capital expenditures 567 (b) 129 61 131 — (12) 876 (b) Six Months 2022: External revenues $ 1,720 $ 968 $ 665 $ 252 $ — $ — $ 3,605 Intersegment revenues 17 1 — 44 — (62) — Net income attributable to Ameren common shareholders 150 100 86 121 (a) 2 — 459 Capital expenditures 806 281 118 332 3 (2) 1,538 Six Months 2021: External revenues $ 1,494 $ 797 $ 515 $ 232 $ — $ — $ 3,038 Intersegment revenues 19 2 — 34 — (55) — Net income attributable to Ameren common shareholders 158 87 83 102 (a) 10 — 440 Capital expenditures 1,101 (b) 286 109 272 1 (6) 1,763 (b) (a) Ameren Transmission earnings reflect an allocation of financing costs from Ameren (parent). (b) Includes $224 million and $417 million at Ameren and Ameren Missouri for wind generation expenditures for the three and six months ended June 30, 2021, respectively. Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2022: External revenues $ 504 $ 184 $ 81 $ — $ 769 Intersegment revenues — — 24 (24) — Net income available to common shareholder 51 6 46 — 103 Capital expenditures 143 69 145 — 357 Three Months 2021: External revenues $ 388 $ 168 $ 73 $ — $ 629 Intersegment revenues — — 15 (15) — Net income available to common shareholder 41 8 37 — 86 Capital expenditures 129 61 119 — 309 Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Six Months 2022: External revenues $ 969 $ 665 $ 159 $ — $ 1,793 Intersegment revenues — — 44 (44) — Net income available to common shareholder 100 86 86 — 272 Capital expenditures 281 118 300 — 699 Six Months 2021: External revenues $ 799 $ 515 $ 138 $ — $ 1,452 Intersegment revenues — — 31 (31) — Net income available to common shareholder 87 83 65 — 235 Capital expenditures 286 109 251 — 646 The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three and six months ended June 30, 2022 and 2021. Economic factors affect the nature, timing, amount, and uncertainty of revenues and cash flows in a similar manner across customer classes. Revenues from alternative revenue programs have a similar distribution among customer classes as revenues from contracts with customers. Other revenues not associated with contracts with customers are presented in the Other customer classification, along with electric transmission and off-system revenues. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Intersegment Eliminations Ameren Three Months 2022: Residential $ 371 $ 284 $ — $ — $ — $ 655 Commercial 298 180 — — — 478 Industrial 73 53 — — — 126 Other 148 (13) — 150 (31) 254 Total electric revenues $ 890 $ 504 $ — $ 150 $ (31) $ 1,513 Residential $ 16 $ — $ 117 $ — $ — $ 133 Commercial 8 — 30 — — 38 Industrial 1 — 11 — — 12 Other 4 — 26 — — 30 Total natural gas revenues $ 29 $ — $ 184 $ — $ — $ 213 Total revenues (a) $ 919 $ 504 $ 184 $ 150 $ (31) $ 1,726 Three Months 2021: Residential $ 328 $ 218 $ — $ — $ — $ 546 Commercial 271 127 — — — 398 Industrial 71 34 — — — 105 Other 119 9 — 136 (29) 235 Total electric revenues $ 789 $ 388 $ — $ 136 $ (29) $ 1,284 Residential $ 11 $ — $ 112 $ — $ — $ 123 Commercial 4 — 29 — — 33 Industrial 1 — 3 — — 4 Other 4 — 24 — — 28 Total natural gas revenues $ 20 $ — $ 168 $ — $ — $ 188 Total revenues (a) $ 809 $ 388 $ 168 $ 136 $ (29) $ 1,472 Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Intersegment Eliminations Ameren Six Months 2022: Residential $ 703 $ 547 $ — $ — $ — $ 1,250 Commercial 538 338 — — — 876 Industrial 130 98 — — — 228 Other 257 (14) — 296 (62) 477 Total electric revenues $ 1,628 $ 969 $ — $ 296 $ (62) $ 2,831 Residential $ 67 $ — $ 486 $ — $ — $ 553 Commercial 30 — 127 — — 157 Industrial 3 — 28 — — 31 Other 9 — 24 — — 33 Total natural gas revenues $ 109 $ — $ 665 $ — $ — $ 774 Total revenues (a) $ 1,737 $ 969 $ 665 $ 296 $ (62) $ 3,605 Six Months 2021: Residential $ 640 $ 447 $ — $ — $ — $ 1,087 Commercial 487 259 — — — 746 Industrial 123 68 — — — 191 Other 180 25 — 266 (55) 416 Total electric revenues $ 1,430 $ 799 $ — $ 266 $ (55) $ 2,440 Residential $ 45 $ — $ 363 $ — $ — $ 408 Commercial 19 — 93 — — 112 Industrial 2 — 17 — — 19 Other 17 — 42 — — 59 Total natural gas revenues $ 83 $ — $ 515 $ — $ — $ 598 Total revenues (a) $ 1,513 $ 799 $ 515 $ 266 $ (55) $ 3,038 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three and six months ended June 30, 2022 and 2021: Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Ameren Three Months 2022: Revenues from alternative revenue programs $ — $ 41 $ 3 $ (4) $ 40 Other revenues not from contracts with customers (36) 1 1 — (34) Three Months 2021: Revenues from alternative revenue programs $ (5) $ 34 $ 2 $ 5 $ 36 Other revenues not from contracts with customers 66 (a) — 1 — 67 (a) Six Months 2022: Revenues from alternative revenue programs $ (6) $ 96 $ (2) $ (3) $ 85 Other revenues not from contracts with customers (36) (a) 3 2 — (31) (a) Six Months 2021: Revenues from alternative revenue programs $ (15) $ 95 $ 5 $ 4 $ 89 Other revenues not from contracts with customers 64 (a) 3 2 — 69 (a) (a) Includes insurance recoveries related to lost sales associated with the Callaway Energy Center maintenance outage. See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for additional information. Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2022: Residential $ 284 $ 117 $ — $ — $ 401 Commercial 180 30 — — 210 Industrial 53 11 — — 64 Other (13) 26 105 (24) 94 Total revenues (a) $ 504 $ 184 $ 105 $ (24) $ 769 Three Months 2021: Residential $ 218 $ 112 $ — $ — $ 330 Commercial 127 29 — — 156 Industrial 34 3 — — 37 Other 9 24 88 (15) 106 Total revenues (a) $ 388 $ 168 $ 88 $ (15) $ 629 Six Months 2022: Residential $ 547 $ 486 $ — $ — $ 1,033 Commercial 338 127 — — 465 Industrial 98 28 — — 126 Other (14) 24 203 (44) 169 Total revenues (a) $ 969 $ 665 $ 203 $ (44) $ 1,793 Six Months 2021: Residential $ 447 $ 363 $ — $ — $ 810 Commercial 259 93 — — 352 Industrial 68 17 — — 85 Other 25 42 169 (31) 205 Total revenues (a) $ 799 $ 515 $ 169 $ (31) $ 1,452 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the Ameren Illinois segments for the three and six months ended June 30, 2022 and 2021: Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Ameren Illinois Three Months 2022: Revenues from alternative revenue programs $ 41 $ 3 $ (3) $ 41 Other revenues not from contracts with customers 1 1 — 2 Three Months 2021: Revenues from alternative revenue programs $ 34 $ 2 $ 2 $ 38 Other revenues not from contracts with customers — 1 — 1 Six Months 2022: Revenues from alternative revenue programs $ 96 $ (2) $ (2) $ 92 Other revenues not from contracts with customers 3 2 — 5 Six Months 2021: Revenues from alternative revenue programs $ 95 $ 5 $ 1 $ 101 Other revenues not from contracts with customers 3 2 — 5

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Nature of Operations	Ameren, headquartered in St. Louis, Missouri, is a public utility holding company whose primary assets are its equity interests in its subsidiaries. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below. Ameren has other subsidiaries that conduct other activities, such as providing shared services. • Union Electric Company, doing business as Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri. • Ameren Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois. • ATXI operates a FERC rate-regulated electric transmission business in the MISO.
Consolidation	Ameren’s and Ameren Missouri’s financial statements are prepared on a consolidated basis and therefore include the accounts of their majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri’s subsidiaries were created for the ownership of renewable generation projects. Ameren Illinois has no subsidiaries. All tabular dollar amounts are in millions, unless otherwise indicated. Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Form 10-K.
Consolidation, Variable Interest Entity, Policy	Variable Interest Entities As of June 30, 2022, and December 31, 2021, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $61 million and $56 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Any earnings or losses related to these investments are included in “Other Income, Net” on Ameren’s consolidated statement of income and comprehensive income. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly affect the activities of these variable interest entities. As of June 30, 2022, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $61 million plus associated outstanding funding commitments of $22 million.
Life Insurance, Corporate Or Bank Owned	Company-owned Life InsuranceAmeren and Ameren Illinois have company-owned life insurance, which is recorded at the net cash surrender value. The net cash surrender value is the amount that can be realized under the insurance policies at the balance sheet date.
Derivatives, Policy	We use derivatives to manage the risk of changes in market prices for natural gas, power, and uranium, as well as the risk of changes in rail transportation surcharges through fuel oil hedges. Such price fluctuations may cause the following: • an unrealized appreciation or depreciation of our contracted commitments to purchase or sell when purchase or sale prices under the commitments are compared with current commodity prices; • market values of natural gas and uranium inventories that differ from the cost of those commodities in inventory; • actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays; and • actual off-system sales revenues that differ from anticipated revenues. The derivatives that we use to hedge these risks are governed by our risk management policies for forward contracts, futures, options, and swaps. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The goal of the hedging program is generally to mitigate financial risks while ensuring that sufficient volumes are available to meet our requirements. Contracts we enter into as part of our risk management program may be settled financially, settled by physical delivery, or net settled with the counterparty. All contracts considered to be derivative instruments are required to be recorded on the balance sheet at their fair values, unless the NPNS exception applies. Many of our physical contracts, such as our purchased power contracts, qualify for the NPNS exception to derivative accounting rules. The revenue or expense on NPNS contracts is recognized at the contract price upon physical delivery. The following disclosures exclude NPNS contracts and other non-derivative commodity contracts that are accounted for under the accrual method of accounting.
Deferred Compensation	Deferred Compensation At June 30, 2022, and December 31, 2021, the present value of benefits to be paid for deferred compensation obligations was $89 million and $91 million, respectively, which was primarily reflected in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet.
Revenue from Contract with Customer	Operating Revenues As of June 30, 2022 and 2021, our remaining performance obligations for contracts with a term greater than one year were immaterial. The Ameren Companies elected not to disclose the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied as of the end of the reporting period for contracts with an initial expected term of one year or less. See Note 14 – Segment Information for disaggregated revenue information.
Excise Taxes	Excise TaxesAmeren Missouri and Ameren Illinois collect from their customers excise taxes, including municipal and state excise taxes and gross receipts taxes that are levied on the sale or distribution of natural gas and electricity.

Short-Term Debt and Liquidity (

Short-Term Debt and Liquidity (Tables)	6 Months Ended
	Jun. 30, 2022
Debt Disclosure [Abstract]
Schedule of Short-term Debt	The following table presents commercial paper outstanding, net of issuance discounts, as of June 30, 2022, and December 31, 2021. There were no borrowings outstanding under the Credit Agreements as of June 30, 2022, or December 31, 2021. June 30, 2022 December 31, 2021 Ameren (parent) $ 595 $ 277 Ameren Missouri 285 165 Ameren Illinois 141 103 Ameren consolidated $ 1,021 $ 545 The following table summarizes the activity and relevant interest rates for Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper issuances and borrowings under the Credit Agreements in the aggregate for the six months ended June 30, 2022 and 2021: Ameren Ameren Ameren Ameren 2022 Average daily amount outstanding $ 374 $ 271 $ 57 $ 702 Weighted-average interest rate 0.87 % 0.65 % 0.47 % 0.75 % Peak amount outstanding during period (a) $ 595 $ 539 $ 142 $ 1,101 Peak interest rate 2.05 % 2.05 % 2.05 % 2.05 % 2021 Average daily amount outstanding $ 388 $ 183 $ 211 $ 782 Weighted-average interest rate 0.24 % 0.22 % 0.22 % 0.23 % Peak amount outstanding during period (a) $ 650 $ 546 $ 485 $ 1,134 Peak interest rate 0.33 % 0.25 % 0.25 % 0.33 % (a) The timing of peak outstanding commercial paper issuances and borrowings under the Credit Agreements varies by company. Therefore, the sum of individual company peak amounts may not equal the Ameren consolidated peak for the period.

Other Income, Net (Tables)

Other Income, Net (Tables)	6 Months Ended
	Jun. 30, 2022
Other Nonoperating Income (Expense) [Abstract]
Other Income And Expenses	The following table presents the components of “Other Income, Net” in the Ameren Companies’ statements of income for the three and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Ameren: Allowance for equity funds used during construction $ 11 $ 9 $ 19 $ 16 Interest income on industrial development revenue bonds 6 6 12 12 Non-service cost components of net periodic benefit income (a) 47 34 93 68 Miscellaneous income 6 7 13 12 Donations (2) (1) (4) (4) Miscellaneous expense (6) (6) (11) (9) Total Other Income, Net $ 62 $ 49 $ 122 $ 95 Ameren Missouri: Allowance for equity funds used during construction $ 6 $ 6 $ 10 $ 10 Interest income on industrial development revenue bonds 6 6 12 12 Non-service cost components of net periodic benefit income (a) 14 14 28 28 Miscellaneous income 1 — 3 1 Donations (1) (1) (2) (1) Miscellaneous expense (2) (1) (4) (3) Total Other Income, Net $ 24 $ 24 $ 47 $ 47 Ameren Illinois: Allowance for equity funds used during construction $ 5 $ 3 $ 9 $ 6 Non-service cost components of net periodic benefit income 21 14 42 28 Miscellaneous income 3 3 5 4 Donations (1) — (2) (3) Miscellaneous expense (3) (4) (5) (5) Total Other Income, Net $ 25 $ 16 $ 49 $ 30 (a) For the three and six months ended June 30, 2022, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $5 million and $11 million, respectively, due to a regulatory tracking mechanism for the difference between the level of such costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. The deferral was $(3) million for both the three and six months ended June 30, 2021. See Note 11– Retirement Benefits for additional information.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2022, and December 31, 2021. As of June 30, 2022, these contracts extended through October 2024, October 2027, May 2032 and March 2024 for fuel oils, natural gas, power and uranium, respectively: Quantity (in millions) June 30, 2022 December 31, 2021 Commodity Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren Fuel oils (in gallons) 21 — 21 30 — 30 Natural gas (in mmbtu) 44 152 196 35 144 179 Power (in MWhs) 3 6 9 6 6 12 Uranium (pounds in thousands) 496 — 496 586 — 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 June 30, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Balance Sheet Location Ameren Ameren Ameren Ameren Ameren Ameren Fuel oils Mark-to-market derivative assets $ 22 $ — $ 22 $ 8 $ — $ 8 Other assets 8 — 8 5 — 5 Natural gas Mark-to-market derivative assets 14 59 73 7 28 35 Other assets 14 27 41 5 13 18 Power Mark-to-market derivative assets 50 9 59 23 — 23 Other assets — 1 1 — — — Uranium Mark-to-market derivative assets 3 — 3 — — — Other assets 1 — 1 1 — 1 Total assets $ 112 $ 96 $ 208 $ 49 $ 41 $ 90 Natural gas Mark-to-market derivative liabilities 4 (a) (a) 2 (a) (a) Other current liabilities — 7 11 — 6 8 Other deferred credits and liabilities 2 4 6 1 2 3 Power Mark-to-market derivative liabilities 141 (a) (a) 50 (a) (a) Other current liabilities — 1 142 — 9 59 Other deferred credits and liabilities 24 53 77 23 108 131 Uranium Mark-to-market derivative liabilities — (a) (a) 1 (a) (a) Other current liabilities — — — — — 1 Total liabilities $ 171 $ 65 $ 236 $ 77 $ 125 $ 202 (a) Balance sheet line item not applicable to registrant.
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 June 30, 2022, and December 31, 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 June 30, 2022 Assets: Ameren Missouri $ 112 $ 36 $ 15 $ 61 Ameren Illinois 96 16 15 65 Ameren $ 208 $ 52 $ 30 $ 126 Liabilities: Ameren Missouri $ 171 $ 36 $ 127 $ 8 Ameren Illinois 65 16 — 49 Ameren $ 236 $ 52 $ 127 $ 57 December 31, 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 “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, 2022, 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: Aggregate Fair Value of Derivative Liabilities (a) Cash Potential Aggregate Amount of Additional Collateral Required (b) Ameren Missouri $ 76 $ 29 $ 12 Ameren Illinois 12 — 4 Ameren $ 88 $ 29 $ 16 (a) Before consideration of master netting arrangements or similar agreements. (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.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2022
Fair Value Disclosures [Abstract]
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 June 30, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Ameren Missouri Derivative assets – commodity contracts: Fuel oils $ 27 $ — $ 3 $ 30 $ 13 $ — $ — $ 13 Natural gas 1 27 — 28 — 12 — 12 Power 21 — 29 50 10 — 13 23 Uranium — — 4 4 — — 1 1 Total derivative assets – commodity contracts $ 49 $ 27 $ 36 $ 112 $ 23 $ 12 $ 14 $ 49 Nuclear decommissioning trust fund: Equity securities: U.S. large capitalization $ 602 $ — $ — $ 602 $ 824 $ — $ — $ 824 Debt securities: U.S. Treasury and agency securities — 173 — 173 — 141 — 141 Corporate bonds — 121 — 121 — 131 — 131 Other — 54 — 54 — 56 — 56 Total nuclear decommissioning trust fund $ 602 $ 348 $ — $ 950 (a) $ 824 $ 328 $ — $ 1,152 (a) Total Ameren Missouri $ 651 $ 375 $ 36 $ 1,062 $ 847 $ 340 $ 14 $ 1,201 Ameren Illinois Derivative assets – commodity contracts: Natural gas $ 5 $ 71 $ 10 $ 86 $ 1 $ 33 $ 7 $ 41 Power — — 10 10 — — — — Total Ameren Illinois $ 5 $ 71 $ 20 $ 96 $ 1 $ 33 $ 7 $ 41 Ameren Derivative assets – commodity contracts (b) $ 54 $ 98 $ 56 $ 208 $ 24 $ 45 $ 21 $ 90 Nuclear decommissioning trust fund (c) 602 348 — 950 (a) 824 328 — 1,152 (a) Total Ameren $ 656 $ 446 $ 56 $ 1,158 $ 848 $ 373 $ 21 $ 1,242 Liabilities: Ameren Missouri Derivative liabilities – commodity contracts: Natural gas $ — $ 4 $ 2 $ 6 $ — $ 2 $ 1 $ 3 Power 100 — 65 165 45 — 28 73 Uranium — — — — — — 1 1 Total Ameren Missouri $ 100 $ 4 $ 67 $ 171 $ 45 $ 2 $ 30 $ 77 June 30, 2022 December 31, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Ameren Illinois Derivative liabilities – commodity contracts: Natural gas $ — $ 6 $ 5 $ 11 $ — $ 5 $ 3 $ 8 Power — — 54 54 — — 117 117 Total Ameren Illinois $ — $ 6 $ 59 $ 65 $ — $ 5 $ 120 $ 125 Ameren Derivative liabilities – commodity contracts (b) $ 100 $ 10 $ 126 $ 236 $ 45 $ 7 $ 150 $ 202 (a) Balance exclude s $7 million of cash and cash equivalents, receivables, payables, and accrued income, net, for both June 30, 2022, and December 31, 2021. (b) See the Ameren Missouri and Ameren Illinois sections of the table for a breakout of the fair value of Ameren’s derivative assets and liabilities by type of commodity. (c) See the Ameren Missouri section of the table for a breakout of the fair value of Ameren’s nuclear decommissioning trust fund by investment type.
Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy	The following table presents the fair value reconciliation of Level 3 power derivative contract assets and liabilities measured at fair value on a recurring basis for the three and six months ended June 30, 2022 and 2021: 2022 2021 Ameren Missouri Ameren Illinois Ameren Ameren Missouri Ameren Illinois Ameren For the three months ended June 30: Beginning balance at April 1 $ (53) $ (74) $ (127) $ (3) $ (185) $ (188) Realized and unrealized gains/(losses) included in regulatory assets/liabilities (5) 32 27 (1) 15 14 Settlements 22 (2) 20 (1) 4 3 Ending balance at June 30 $ (36) $ (44) $ (80) $ (5) $ (166) $ (171) Change in unrealized gains/(losses) related to assets/liabilities held at June 30 $ 2 $ 30 $ 32 $ (2) $ 15 $ 13 For the six months ended June 30: Beginning balance at January 1 $ (15) $ (117) $ (132) $ 2 $ (198) $ (196) Realized and unrealized gains/(losses) included in regulatory assets/liabilities (45) 74 29 (6) 24 18 Settlements 24 (1) 23 (1) 8 7 Ending balance at June 30 $ (36) $ (44) $ (80) $ (5) $ (166) $ (171) Change in unrealized gains/(losses) related to assets/liabilities held at June 30 $ (36) $ 72 $ 36 $ (3) $ 24 $ 21
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques	The following table describes the valuation techniques and significant unobservable inputs utilized for the fair value of our Level 3 power derivative contract assets and liabilities as of June 30, 2022, and December 31, 2021: Fair Value Weighted Average (b) Commodity Assets Liabilities Valuation Technique(s) Unobservable Input (a) Range 2022 Power (c) $ 39 $ (119) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 36 – 122 65 Nodal basis ($/MWh) (17) – 3 (6) Trend rate (%) 0 – 3 2 2021 Power (d) $ 13 $ (145) Discounted cash flow Average forward peak and off-peak pricing – forwards/swaps ($/MWh) 32 – 55 40 Nodal basis ($/MWh) (14) – 0 (2) Trend rate (%) (e) 0 (a) Generally, significant increases (decreases) in these inputs in isolation would result in a significantly higher (lower) fair value measurement. (b) Unobservable inputs were weighted by relative fair value. (c) Valuations through 2031 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2031 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials. (d) Valuations through 2029 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2029 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials. (e) No meaningful range around weighted average.
Schedule of Financial Assets and Liabilities	The following table sets forth the carrying amount and, by level within the fair value hierarchy, the fair value of financial assets and liabilities disclosed, but not recorded, at fair value as of June 30, 2022, and December 31, 2021: Carrying Fair Value Level 1 Level 2 Level 3 Total June 30, 2022 Ameren: Cash, cash equivalents, and restricted cash $ 161 $ 161 $ — $ — $ 161 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 1,021 — 1,021 — 1,021 Long-term debt (including current portion) (a) 13,590 (b) — 12,016 500 (c) 12,516 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 7 $ 7 $ — $ — $ 7 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 285 — 285 — 285 Long-term debt (including current portion) (a) 6,139 (b) — 5,641 — 5,641 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 146 $ 146 $ — $ — $ 146 Short-term debt 141 — 141 — 141 Long-term debt (including current portion) 4,394 (b) — 4,037 — 4,037 December 31, 2021 Ameren: Cash, cash equivalents, and restricted cash $ 155 $ 155 $ — $ — $ 155 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 545 — 545 — 545 Long-term debt (including current portion) (a) 13,067 (b) — 13,930 591 (c) 14,521 Ameren Missouri: Cash, cash equivalents, and restricted cash $ 8 $ 8 $ — $ — $ 8 Investments in industrial development revenue bonds (a) 248 — 248 — 248 Short-term debt 165 — 165 — 165 Long-term debt (including current portion) (a) 5,619 (b) — 6,321 — 6,321 Ameren Illinois: Cash, cash equivalents, and restricted cash $ 133 $ 133 $ — $ — $ 133 Short-term debt 103 — 103 — 103 Long-term debt (including current portion) 4,392 (b) — 4,971 — 4,971 (a) Ameren and Ameren Missouri have investments in industrial development revenue bonds, classified as held-to-maturity and recorded in “Other Assets,” that are equal to the finance obligations for the Peno Creek and Audrain CT energy centers. As of June 30, 2022, and December 31, 2021, the carrying amount of both the investments in industrial development revenue bonds and the finance obligations approximated fair value. (b) Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $97 million, $43 million, and $37 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of June 30, 2022. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $94 million, $38 million, and $39 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2021. (c) The Level 3 fair value amount consists of ATXI’s senior unsecured notes.

Related Party Transactions (Tab

Related Party Transactions (Tables)	6 Months Ended
	Jun. 30, 2022
Related Party Transactions [Abstract]
Schedule of Affiliate Receivables and Payables	The following table presents the affiliate balances related to income taxes for Ameren Missouri and Ameren Illinois as of June 30, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Ameren Missouri Ameren Illinois Ameren Missouri Ameren Illinois Income taxes payable to parent (a) $ — $ 82 $ — $ 8 Income taxes receivable from parent (b) 45 — 27 18 (a) Included in “Accounts payable – affiliates” on the balance sheet. (b) Included in “Accounts receivable – affiliates” on the balance sheet.
Schedule of Related Party Transactions	The following table presents the impact on Ameren Missouri and Ameren Illinois of related-party transactions for the three and six months ended June 30, 2022 and 2021: Three Months Six Months Agreement Income Statement Ameren Ameren Ameren Ameren Ameren Missouri power supply Operating Revenues 2022 $ 1 $ (a) $ 5 $ (a) agreements with Ameren Illinois 2021 3 (a) 5 (a) Ameren Missouri and Ameren Illinois Operating Revenues 2022 $ 6 $ (b) $ 12 $ (b) rent and facility services 2021 7 (b) 14 (b) Ameren Missouri and Ameren Illinois miscellaneous Operating Revenues 2022 $ (b) $ (b) $ (b) $ 1 support services and other services provided to ATXI 2021 (b) 2 (b) 2 Total Operating Revenues 2022 $ 7 $ (b) $ 17 $ 1 2021 10 2 19 2 Ameren Illinois power supply Purchased Power 2022 $ (a) $ 1 $ (a) $ 5 agreements with Ameren Missouri 2021 (a) 3 (a) 5 Ameren Missouri and Ameren Illinois Purchased Power 2022 $ (b) $ (b) $ (b) $ (b) transmission services from ATXI 2021 1 1 2 1 Total Purchased Power 2022 $ (b) $ 1 $ (b) $ 5 2021 1 4 2 6 Ameren Missouri and Ameren Illinois Other Operations and Maintenance 2022 $ (b) $ (b) $ (b) $ 1 rent and facility services 2021 (b) 1 (b) 2 Ameren Services support services Other Operations and Maintenance 2022 $ 33 $ 32 $ 71 $ 67 agreement 2021 34 31 69 64 Total Other Operations and 2022 $ 33 $ 32 $ 71 $ 68 Maintenance 2021 34 32 69 66 Money pool borrowings (advances) (Interest Charges)/Other Income, Net 2022 $ (b) $ (b) $ (b) $ (b) 2021 (b) (b) (b) (b) (a) Not applicable. (b) Amount less than $1 million.

Callaway Energy Center (Tables)

Callaway Energy Center (Tables)	6 Months Ended
	Jun. 30, 2022
Nuclear Waste Matters [Abstract]
Schedule of Insurance Coverage at Callaway Energy Center	The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at June 30, 2022: Type and Source of Coverage Most Recent Maximum Coverages Maximum Assessments Public liability and nuclear worker liability: American Nuclear Insurers January 1, 2022 $ 450 $ — Pool participation (a) 13,073 (a) 138 (b) $ 13,523 (c) $ 138 Property damage: NEIL and EMANI April 1, 2022 $ 3,200 (d) $ 26 (e) Accidental outage: NEIL April 1, 2022 $ 490 (f) $ 7 (e) (a) Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the program. (b) Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $450 million in the event of an incident at any licensed United States commercial reactor, payable at $21 million per year. (c) Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. This limit is subject to change to account for the effects of inflation and changes in the number of licensed power reactors. (d) NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $2.3 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events. (e) All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL. (f) Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are limited to $328 million.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2022
Retirement Benefits [Abstract]
Components Of Net Periodic Benefit Cost	The following table presents the components of the net periodic benefit cost (income) incurred for Ameren’s pension and postretirement benefit plans for the three and six months ended June 30, 2022 and 2021: Pension Benefits Postretirement Benefits Three Months Six Months Three Months Six Months 2022 2021 2022 2021 2022 2021 2022 2021 Service cost (a) $ 31 $ 34 $ 64 $ 67 $ 5 $ 6 $ 10 $ 12 Non-service cost components: Interest cost 41 38 81 76 9 8 17 16 Expected return on plan assets (80) (74) (160) (149) (22) (20) (43) (40) Amortization of: Prior service benefit — — — — (1) (1) (2) (2) Actuarial loss (gain) 6 20 12 37 (5) (2) (9) (3) Total non-service cost components (b) $ (33) $ (16) $ (67) $ (36) $ (19) $ (15) $ (37) $ (29) Net periodic benefit cost (income) (c) $ (2) $ 18 $ (3) $ 31 $ (14) $ (9) $ (27) $ (17) (a) Service cost, net of capitalization, is reflected in “Operating Expenses – Other operations and maintenance” on Ameren’s statement of income. (b) Non-service cost components are reflected in “Other Income, Net” on Ameren’s statement of income. See Note 5 – Other Income, Net, for additional information. (c) Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
Summary Of Benefit Plan Costs Incurred	Ameren Missouri and Ameren Illinois are responsible for their respective share of Ameren’s pension and other postretirement costs. The following table presents the respective share of net periodic pension and other postretirement benefit costs (income) incurred for the three and six months ended June 30, 2022 and 2021: Pension Benefits Postretirement Benefits Three Months Six Months Three Months Six Months 2022 2021 2022 2021 2022 2021 2022 2021 Ameren Missouri (a) $ (1) $ 9 $ (2) $ 15 $ (4) $ (1) $ (7) $ (2) Ameren Illinois — 9 1 17 (10) (8) (20) (15) Other (1) — (2) (1) — — — — Ameren (a) $ (2) $ 18 $ (3) $ 31 $ (14) $ (9) $ (27) $ (17) (a) Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2022
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three and six months ended June 30, 2022 and 2021: Ameren Ameren Missouri Ameren Illinois 2022 2021 2022 2021 2022 2021 Three Months Federal statutory corporate income tax rate 21 % 21 % 21 % 21 % 21 % 21 % Increases (decreases) from: Amortization of deferred investment tax credit — — (1) (1) — — Amortization of excess deferred taxes (a) (8) (9) (15) (17) (2) (2) Depreciation differences — — — 1 (1) 1 Other 1 — — — — — Renewable and other tax credits (b) (4) (4) (10) (10) — (1) State tax 5 5 3 3 7 7 Effective income tax rate 15 % 13 % (2) % (3) % 25 % 26 % Six Months Federal statutory corporate income tax rate 21 % 21 % 21 % 21 % 21 % 21 % Increases (decreases) from: Amortization of deferred investment tax credit — — (1) (1) — — Amortization of excess deferred taxes (a) (8) (9) (16) (17) (2) (3) Depreciation differences — — — 1 — — Renewable and other tax credits (b) (5) (5) (10) (10) — — State tax 5 5 3 3 7 7 Effective income tax rate 13 % 12 % (3) % (3) % 26 % 25 % (a) Reflects the amortization of amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. Deferred income taxes are revalued when federal or state income tax rates change, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory asset or liability. (b) Includes credits associated with the High Prairie and Atchison renewable energy centers. Ameren Missouri placed the High Prairie Renewable Energy Center in service in December 2020. Additionally, Ameren Missouri placed in service the wind turbines at its Atchison Renewable Energy Center throughout the first half of 2021. The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.

Supplemental Information (Table

Supplemental Information (Tables)	6 Months Ended
	Jun. 30, 2022
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 at June 30, 2022, and December 31, 2021: June 30, 2022 December 31, 2021 Ameren Ameren Ameren Ameren Ameren Ameren “Cash and cash equivalents” $ 7 $ — $ — $ 8 $ — $ — Restricted cash included in “Other current assets” 7 2 4 16 4 6 Restricted cash included in “Other assets” 142 — 142 127 — 127 Restricted cash included in “Nuclear decommissioning trust fund” 5 5 — 4 4 — Total cash, cash equivalents, and restricted cash $ 161 $ 7 $ 146 $ 155 $ 8 $ 133
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 and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Ameren: Beginning of period $ 28 $ 47 $ 29 $ 50 Bad debt expense 7 (3) 11 1 Net write-offs (5) (2) (10) (9) End of period $ 30 $ 42 $ 30 $ 42 Ameren Missouri: Beginning of period $ 11 $ 15 $ 13 $ 16 Bad debt expense 2 2 3 3 Net write-offs (1) (1) (4) (3) End of period $ 12 $ 16 $ 12 $ 16 Ameren Illinois: (a) Beginning of period $ 17 $ 32 $ 16 $ 34 Bad debt expense 5 (5) (b) 8 (2) (b) Net write-offs (4) (1) (6) (6) End of period $ 18 $ 26 $ 18 $ 26 (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. (b) In the three and six months ended June 30, 2021, Ameren Illinois’ bad debt expense was reduced as a result of state funding received for customer bill assistance.
Schedule of Cash Flow, Supplemental Disclosures	The following table provides noncash financing and investing activity excluded from the statements of cash flows for the six months ended June 30, 2022 and 2021: June 30, 2022 June 30, 2021 Ameren Ameren Ameren Ameren Ameren Ameren Investing Accrued capital expenditures $ 408 $ 204 $ 193 $ 434 $ 259 $ 174 Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund (211) (211) — 85 85 — Financing Issuance of common stock for stock-based compensation $ 31 $ — $ — $ 33 $ — $ — Issuance of common stock under the DRPlus 8 — — — — —
Asset Retirement Obligation Disclosure	The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the six months ended June 30, 2022: Ameren Ameren Ameren Balance at December 31, 2021 $ 760 (a) $ 4 (b) $ 764 (a) Accretion 15 (c) — 15 (c) Change in estimates 2 — 2 Balance at June 30, 2022 $ 777 (a) $ 4 (b) $ 781 (a) (a) Balance included $7 million in “Other current liabilities” on the balance sheet as of both June 30, 2022, and December 31, 2021. (b) Included in “Other deferred credits and liabilities” on the balance sheet. (c) Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.
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 and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Ameren Missouri $ 39 $ 35 $ 73 $ 66 Ameren Illinois 28 27 73 66 Ameren $ 67 $ 62 $ 146 $ 132
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 and six months ended June 30, 2022 and 2021: Three Months Six Months 2022 2021 2022 2021 Weighted-average Common Shares Outstanding – Basic 258.2 256.1 258.0 255.2 Assumed settlement of performance share units and restricted stock units 1.0 1.1 1.1 1.3 Dilutive effect of forward sale agreements 0.2 — 0.1 — Weighted-average Common Shares Outstanding – Diluted (a) 259.4 257.2 259.2 256.5 (a) There was an immaterial number of anti-dilutive securities excluded from the earnings per diluted share calculations for the three and six months ended June 30, 2022. There were no anti-dilutive securities excluded from the earnings per diluted share calculations for the three and six months ended June 30, 2021.

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2022
Segment Reporting [Abstract]
Schedule Of Segment Reporting Information By Segment	The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three and six months ended June 30, 2022 and 2021. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount. For additional information about our segments, see Note 16 – Segment Information under Part II, Item 8, of the Form 10-K. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Other Intersegment Eliminations Ameren Three Months 2022: External revenues $ 912 $ 504 $ 184 $ 126 $ — $ — $ 1,726 Intersegment revenues 7 — — 24 — (31) — Net income (loss) attributable to Ameren common shareholders 100 51 6 63 (a) (13) — 207 Capital expenditures 392 143 69 160 1 (1) 764 Three Months 2021: External revenues $ 799 $ 386 $ 168 $ 119 $ — $ — $ 1,472 Intersegment revenues 10 2 — 17 — (29) — Net income (loss) attributable to Ameren common shareholders 111 41 8 55 (a) (8) — 207 Capital expenditures 567 (b) 129 61 131 — (12) 876 (b) Six Months 2022: External revenues $ 1,720 $ 968 $ 665 $ 252 $ — $ — $ 3,605 Intersegment revenues 17 1 — 44 — (62) — Net income attributable to Ameren common shareholders 150 100 86 121 (a) 2 — 459 Capital expenditures 806 281 118 332 3 (2) 1,538 Six Months 2021: External revenues $ 1,494 $ 797 $ 515 $ 232 $ — $ — $ 3,038 Intersegment revenues 19 2 — 34 — (55) — Net income attributable to Ameren common shareholders 158 87 83 102 (a) 10 — 440 Capital expenditures 1,101 (b) 286 109 272 1 (6) 1,763 (b) (a) Ameren Transmission earnings reflect an allocation of financing costs from Ameren (parent). (b) Includes $224 million and $417 million at Ameren and Ameren Missouri for wind generation expenditures for the three and six months ended June 30, 2021, respectively. Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2022: External revenues $ 504 $ 184 $ 81 $ — $ 769 Intersegment revenues — — 24 (24) — Net income available to common shareholder 51 6 46 — 103 Capital expenditures 143 69 145 — 357 Three Months 2021: External revenues $ 388 $ 168 $ 73 $ — $ 629 Intersegment revenues — — 15 (15) — Net income available to common shareholder 41 8 37 — 86 Capital expenditures 129 61 119 — 309 Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Six Months 2022: External revenues $ 969 $ 665 $ 159 $ — $ 1,793 Intersegment revenues — — 44 (44) — Net income available to common shareholder 100 86 86 — 272 Capital expenditures 281 118 300 — 699 Six Months 2021: External revenues $ 799 $ 515 $ 138 $ — $ 1,452 Intersegment revenues — — 31 (31) — Net income available to common shareholder 87 83 65 — 235 Capital expenditures 286 109 251 — 646
Disaggregation of Revenue	The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three and six months ended June 30, 2022 and 2021. Economic factors affect the nature, timing, amount, and uncertainty of revenues and cash flows in a similar manner across customer classes. Revenues from alternative revenue programs have a similar distribution among customer classes as revenues from contracts with customers. Other revenues not associated with contracts with customers are presented in the Other customer classification, along with electric transmission and off-system revenues. Ameren Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Intersegment Eliminations Ameren Three Months 2022: Residential $ 371 $ 284 $ — $ — $ — $ 655 Commercial 298 180 — — — 478 Industrial 73 53 — — — 126 Other 148 (13) — 150 (31) 254 Total electric revenues $ 890 $ 504 $ — $ 150 $ (31) $ 1,513 Residential $ 16 $ — $ 117 $ — $ — $ 133 Commercial 8 — 30 — — 38 Industrial 1 — 11 — — 12 Other 4 — 26 — — 30 Total natural gas revenues $ 29 $ — $ 184 $ — $ — $ 213 Total revenues (a) $ 919 $ 504 $ 184 $ 150 $ (31) $ 1,726 Three Months 2021: Residential $ 328 $ 218 $ — $ — $ — $ 546 Commercial 271 127 — — — 398 Industrial 71 34 — — — 105 Other 119 9 — 136 (29) 235 Total electric revenues $ 789 $ 388 $ — $ 136 $ (29) $ 1,284 Residential $ 11 $ — $ 112 $ — $ — $ 123 Commercial 4 — 29 — — 33 Industrial 1 — 3 — — 4 Other 4 — 24 — — 28 Total natural gas revenues $ 20 $ — $ 168 $ — $ — $ 188 Total revenues (a) $ 809 $ 388 $ 168 $ 136 $ (29) $ 1,472 Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Intersegment Eliminations Ameren Six Months 2022: Residential $ 703 $ 547 $ — $ — $ — $ 1,250 Commercial 538 338 — — — 876 Industrial 130 98 — — — 228 Other 257 (14) — 296 (62) 477 Total electric revenues $ 1,628 $ 969 $ — $ 296 $ (62) $ 2,831 Residential $ 67 $ — $ 486 $ — $ — $ 553 Commercial 30 — 127 — — 157 Industrial 3 — 28 — — 31 Other 9 — 24 — — 33 Total natural gas revenues $ 109 $ — $ 665 $ — $ — $ 774 Total revenues (a) $ 1,737 $ 969 $ 665 $ 296 $ (62) $ 3,605 Six Months 2021: Residential $ 640 $ 447 $ — $ — $ — $ 1,087 Commercial 487 259 — — — 746 Industrial 123 68 — — — 191 Other 180 25 — 266 (55) 416 Total electric revenues $ 1,430 $ 799 $ — $ 266 $ (55) $ 2,440 Residential $ 45 $ — $ 363 $ — $ — $ 408 Commercial 19 — 93 — — 112 Industrial 2 — 17 — — 19 Other 17 — 42 — — 59 Total natural gas revenues $ 83 $ — $ 515 $ — $ — $ 598 Total revenues (a) $ 1,513 $ 799 $ 515 $ 266 $ (55) $ 3,038 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three and six months ended June 30, 2022 and 2021: Ameren Missouri Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Transmission Ameren Three Months 2022: Revenues from alternative revenue programs $ — $ 41 $ 3 $ (4) $ 40 Other revenues not from contracts with customers (36) 1 1 — (34) Three Months 2021: Revenues from alternative revenue programs $ (5) $ 34 $ 2 $ 5 $ 36 Other revenues not from contracts with customers 66 (a) — 1 — 67 (a) Six Months 2022: Revenues from alternative revenue programs $ (6) $ 96 $ (2) $ (3) $ 85 Other revenues not from contracts with customers (36) (a) 3 2 — (31) (a) Six Months 2021: Revenues from alternative revenue programs $ (15) $ 95 $ 5 $ 4 $ 89 Other revenues not from contracts with customers 64 (a) 3 2 — 69 (a) (a) Includes insurance recoveries related to lost sales associated with the Callaway Energy Center maintenance outage. See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for additional information. Ameren Illinois Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Intersegment Eliminations Ameren Illinois Three Months 2022: Residential $ 284 $ 117 $ — $ — $ 401 Commercial 180 30 — — 210 Industrial 53 11 — — 64 Other (13) 26 105 (24) 94 Total revenues (a) $ 504 $ 184 $ 105 $ (24) $ 769 Three Months 2021: Residential $ 218 $ 112 $ — $ — $ 330 Commercial 127 29 — — 156 Industrial 34 3 — — 37 Other 9 24 88 (15) 106 Total revenues (a) $ 388 $ 168 $ 88 $ (15) $ 629 Six Months 2022: Residential $ 547 $ 486 $ — $ — $ 1,033 Commercial 338 127 — — 465 Industrial 98 28 — — 126 Other (14) 24 203 (44) 169 Total revenues (a) $ 969 $ 665 $ 203 $ (44) $ 1,793 Six Months 2021: Residential $ 447 $ 363 $ — $ — $ 810 Commercial 259 93 — — 352 Industrial 68 17 — — 85 Other 25 42 169 (31) 205 Total revenues (a) $ 799 $ 515 $ 169 $ (31) $ 1,452 (a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the Ameren Illinois segments for the three and six months ended June 30, 2022 and 2021: Ameren Illinois Electric Distribution Ameren Illinois Natural Gas Ameren Illinois Transmission Ameren Illinois Three Months 2022: Revenues from alternative revenue programs $ 41 $ 3 $ (3) $ 41 Other revenues not from contracts with customers 1 1 — 2 Three Months 2021: Revenues from alternative revenue programs $ 34 $ 2 $ 2 $ 38 Other revenues not from contracts with customers — 1 — 1 Six Months 2022: Revenues from alternative revenue programs $ 96 $ (2) $ (2) $ 92 Other revenues not from contracts with customers 3 2 — 5 Six Months 2021: Revenues from alternative revenue programs $ 95 $ 5 $ 1 $ 101 Other revenues not from contracts with customers 3 2 — 5

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Basis Of Presentation And Significant Accounting Policies [Line Items]
Unconsolidated variable interest	$ 61	$ 56
Cash Surrender Value of Life Insurance	244	278
Corporate owned life insurance, borrowings	108	109
Ameren Illinois Company
Basis Of Presentation And Significant Accounting Policies [Line Items]
Cash Surrender Value of Life Insurance	115	117
Corporate owned life insurance, borrowings	108	$ 109
Partnership Funding Commitment
Basis Of Presentation And Significant Accounting Policies [Line Items]
Outstanding funding commitments	$ 22

Rate And Regulatory Matters (Na

Rate And Regulatory Matters (Narrative-Missouri) (Details) - Union Electric Company $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 MWh	Mar. 31, 2022 MWh	Jun. 30, 2022 USD ($) numberOfCountriesInvestigatedByTheDOC
Rate And Regulatory Matters [Line Items]
Missouri Renewable Energy Standard Percentage			15%
Missouri Renewable Energy Standard Percentage - Solar			2%
Number of Countries Investigated by the DOC | numberOfCountriesInvestigatedByTheDOC			4
Pending Rate Case | Electric
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 316
Public Utilities, Requested Return on Equity, Percentage			10.20%
Public Utilities, Requested Equity Capital Structure, Percentage			51.90%
Rate Base			$ 11,600
Months to complete a rate proceeding			11 months
Wind Generation Facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts | MWh	200	150
Maximum
Rate And Regulatory Matters [Line Items]
PISA Rate Increase Limit Beginning 2024			2.50%
Public Utilities, Approved Rate Increase (Decrease), Percentage			2.85%
Percentage of energy sourced from renewable resources			100%

Rate And Regulatory Matters (_2

Rate And Regulatory Matters (Narrative-Illinois) (Details) - Ameren Illinois Company $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) numberOfProposedPerformanceMetrics
Rate And Regulatory Matters [Line Items]
Annual investment in energy-efficiency programs	$ 120
Minimum
Rate And Regulatory Matters [Line Items]
ICC required RTO cost benefit study duration	5 years
Maximum
Rate And Regulatory Matters [Line Items]
ICC required RTO cost benefit study duration	10 years
Electric Distribution
Rate And Regulatory Matters [Line Items]
Requested Return on Equity Adjustment	0.24%
Number of Proposed Performance Metrics | numberOfProposedPerformanceMetrics	8
Electric Distribution | Minimum
Rate And Regulatory Matters [Line Items]
Return on equity adjustment	0.20%
ICC Staff Recommended Return on Equity Adjustment	0.20%
Electric Distribution | Maximum
Rate And Regulatory Matters [Line Items]
Return on equity adjustment	0.60%
ICC Staff Recommended Return on Equity Adjustment	0.24%
Pending Rate Case | Electric Distribution | IEIMA
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 84
Public Utilities, Requested Equity Capital Structure, Percentage	54%
ICC Staff Recommended Rate Increase (Decrease)	$ 60
ICC Staff Recommended Equity Capital Structure, Percentage	50%
Pending Rate Case | Electric Distribution | FEJA energy-efficiency rider
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 17
Pending Rate Case | Natural gas
Rate And Regulatory Matters [Line Items]
Natural Gas Capital Investment Prudency Challenge	70
Challenged Recoveries Under the QIP	3
IETL
Rate And Regulatory Matters [Line Items]
Energy Transition Assistance Fund Surcharge	$ 50

Rate And Regulatory Matters (_3

Rate And Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended
	May 31, 2020	Jun. 30, 2022	Dec. 31, 2021
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		$ 5,727	$ 5,848
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		2,484	$ 2,374
Final Rate Order | Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		$ 9
Midwest Independent Transmission System Operator, Inc | Final Rate Order
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage	10.02%

Short-Term Debt And Liquidity_2

Short-Term Debt And Liquidity (Narrative) (Details) $ in Billions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021	Jun. 30, 2022 USD ($)	Jun. 30, 2021
Credit Agreements
Short-term Debt [Line Items]
Net Liquidity Available	$ 1.3		$ 1.3
Actual debt-to-capital ratio	0.59		0.59
Utilities
Short-term Debt [Line Items]
Short-term Debt, Weighted Average Interest Rate, over Time	0.98%	0.22%	0.69%	0.22%
Union Electric Company | Missouri Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.51		0.51
Ameren Illinois Company | Illinois Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.44		0.44

Short-Term Debt and Liquidity_3

Short-Term Debt and Liquidity (Short-Term Debt outstanding) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Short-term Debt [Line Items]
Short-term debt	$ 1,021	$ 545
Union Electric Company
Short-term Debt [Line Items]
Short-term debt	285	165
Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	141	103
Commercial Paper
Short-term Debt [Line Items]
Short-term debt	1,021	545
Commercial Paper | Parent Company
Short-term Debt [Line Items]
Short-term debt	595	277
Commercial Paper | Union Electric Company
Short-term Debt [Line Items]
Short-term debt	285	165
Commercial Paper | Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	$ 141	$ 103

Short-Term Debt and Liquidity_4

Short-Term Debt and Liquidity (Short-Term Debt Activity) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Short-term Debt [Line Items]
Average daily amount outstanding	$ 702	$ 782
Weighted-average interest rate	0.75%	0.23%
Short-term Debt, Maximum Amount Outstanding During Period	$ 1,101	$ 1,134
Peak interest rate	2.05%	0.33%
Parent Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 374	$ 388
Weighted-average interest rate	0.87%	0.24%
Short-term Debt, Maximum Amount Outstanding During Period	$ 595	$ 650
Peak interest rate	2.05%	0.33%
Union Electric Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 271	$ 183
Weighted-average interest rate	0.65%	0.22%
Short-term Debt, Maximum Amount Outstanding During Period	$ 539	$ 546
Peak interest rate	2.05%	0.25%
Ameren Illinois Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 57	$ 211
Weighted-average interest rate	0.47%	0.22%
Short-term Debt, Maximum Amount Outstanding During Period	$ 142	$ 485
Peak interest rate	2.05%	0.25%

Long-Term debt and Equity Fin_2

Long-Term debt and Equity Financings (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended			3 Months Ended			6 Months Ended
	Aug. 31, 2022 USD ($)	Jul. 31, 2022 $ / shares shares	Apr. 30, 2022 USD ($)	Jun. 30, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares	Jun. 30, 2021 shares	Jun. 30, 2022 USD ($) $ / shares shares	Jun. 30, 2021 USD ($) shares	Dec. 31, 2022 USD ($)	Jul. 12, 2022 shares	May 31, 2021 USD ($)
Long-Term Debt And Equity Financings [Line Items]
Shares issued under the DRPlus and 401(k) plan | shares				0.2		0.2	0.3	0.3
Stock Issued During Period, Shares, Other | shares				0	0.4	0	0.4	0.5
Stock Issued During Period, Value, Other					$ 31
Maximum Value Of Shares To Be Issued Under ATM Program											$ 750
Value of Shares Available to be Issued Under ATM Program				$ 90			$ 90
Forward Contract Indexed to Issuer's Equity, Basis Spread				75			75
Issuances of common stock							$ 17	$ 258
Minimum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares							$ 86.35
Maximum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares							94.80
Weighted Average
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares							$ 89.78
Dividend reinvestment and 401 (k) plans
Long-Term Debt And Equity Financings [Line Items]
Issuances of common stock				$ 4			$ 17
Accrued Proceeds from Issuance of Common Stock							$ 8
Forward Sale Agreements Outstanding
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value | shares				5.6			5.6
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value				$ 500			$ 500
Period End Net Cash Settlement Price				8			8
Period End Net Share Settlement Price				0.1			0.1
Forward Sale Agreement Equity Offering Shares				5.6			5.6
Forward Sale Agreement Gross Sales Price				510			510
Forward Sale Agreement, Compensation Received by Counterparty				5			5
Subsequent Event | Forward Sale Agreements Outstanding
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Indexed Shares (in shares) | shares		5.8
Forward Contract Indexed tp Issuer's Equity, Expected Settlement									$ 300
Subsequent Event | April 1, 2022 Forward Sale
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Indexed Shares (in shares) | shares										0.2
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares		$ 90.77
Union Electric Company | Secured Debt | Senior Secured Notes 3.90% Due 2052
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount			$ 525
Debt Instrument, Interest Rate, Stated Percentage			3.90%
Proceeds from Issuance of Secured Debt			$ 519
Ameren Transmission Company of Illinois | Unsecured Debt | Senior Unsecured Notes, 2.96%, Due 2052
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount				$ 95			$ 95
Debt Instrument, Interest Rate, Stated Percentage				2.96%			2.96%
Ameren Transmission Company of Illinois | Unsecured Debt | Senior Unsecured Notes, 2.96%, Due 2052 | Subsequent Event
Long-Term Debt And Equity Financings [Line Items]
Proceeds from Issuance of Debt	$ 95
Ameren Transmission Company of Illinois | Unsecured Debt | Senior Unsecured Notes, 3.43%, Due 2050
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				3.43%			3.43%
Long-Term Debt, Maturity, Year One				$ 50			$ 50

Other Income, Net (Details)

Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 11	$ 9	$ 19	$ 16
Interest income on industrial development revenue bonds	6	6	12	12
Non-service cost components of net periodic benefit income	47	34	93	68
Miscellaneous income	6	7	13	12
Donations	(2)	(1)	(4)	(4)
Miscellaneous expense	(6)	(6)	(11)	(9)
Total Other Income, Net	62	49	122	95
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	6	6	10	10
Interest income on industrial development revenue bonds	6	6	12	12
Non-service cost components of net periodic benefit income	14	14	28	28
Miscellaneous income	1	0	3	1
Donations	(1)	(1)	(2)	(1)
Miscellaneous expense	(2)	(1)	(4)	(3)
Total Other Income, Net	24	24	47	47
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	5		11	(3)
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	5	3	9	6
Non-service cost components of net periodic benefit income	21	14	42	28
Miscellaneous income	3	3	5	4
Donations	(1)	0	(2)	(3)
Miscellaneous expense	(3)	(4)	(5)	(5)
Total Other Income, Net	$ 25	$ 16	$ 49	$ 30

Derivative Financial Instrume_3

Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail) lb in Thousands, gal in Millions, MWh in Millions, MMBTU in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2022 MWh MMBTU lb gal	Dec. 31, 2021 MWh MMBTU lb gal
Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	21	30
Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	196	179
Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh	9	12
Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	496	586
Union Electric Company | Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	21	30
Union Electric Company | Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	44	35
Union Electric Company | Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh	3	6
Union Electric Company | Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	496	586
Ameren Illinois Company | Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	0	0
Ameren Illinois Company | Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	152	144
Ameren Illinois Company | Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh	6	6
Ameren Illinois Company | Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	0	0

Derivative Financial Instrume_4

Derivative Financial Instruments (Derivative Instruments Carrying Value) (Detail) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Derivative assets	$ 208	$ 90
Derivative Liability	236	202
Fuel oils | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	22	8
Fuel oils | Other assets
Derivative [Line Items]
Derivative assets	8	5
Natural gas | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	73	35
Natural gas | Other assets
Derivative [Line Items]
Derivative assets	41	18
Natural gas | Other current liabilities
Derivative [Line Items]
Derivative Liability	11	8
Natural gas | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	6	3
Power | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	59	23
Power | Other assets
Derivative [Line Items]
Derivative assets	1	0
Power | Other current liabilities
Derivative [Line Items]
Derivative Liability	142	59
Power | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	77	131
Uranium | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	3	0
Uranium | Other assets
Derivative [Line Items]
Derivative assets	1	1
Uranium | Other current liabilities
Derivative [Line Items]
Derivative Liability	0	1
Union Electric Company
Derivative [Line Items]
Derivative assets	112	49
Derivative Liability	171	77
Union Electric Company | Fuel oils | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	22	8
Union Electric Company | Fuel oils | Other assets
Derivative [Line Items]
Derivative assets	8	5
Union Electric Company | Natural gas | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	14	7
Union Electric Company | Natural gas | Other assets
Derivative [Line Items]
Derivative assets	14	5
Union Electric Company | Natural gas | Mark-to-market derivative liabilities
Derivative [Line Items]
Derivative Liability	4	2
Union Electric Company | Natural gas | Other current liabilities
Derivative [Line Items]
Derivative Liability	0	0
Union Electric Company | Natural gas | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	2	1
Union Electric Company | Power | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	50	23
Union Electric Company | Power | Other assets
Derivative [Line Items]
Derivative assets	0	0
Union Electric Company | Power | Mark-to-market derivative liabilities
Derivative [Line Items]
Derivative Liability	141	50
Union Electric Company | Power | Other current liabilities
Derivative [Line Items]
Derivative Liability	0	0
Union Electric Company | Power | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	24	23
Union Electric Company | Uranium | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	3	0
Union Electric Company | Uranium | Other assets
Derivative [Line Items]
Derivative assets	1	1
Union Electric Company | Uranium | Mark-to-market derivative liabilities
Derivative [Line Items]
Derivative Liability	0	1
Union Electric Company | Uranium | Other current liabilities
Derivative [Line Items]
Derivative Liability	0	0
Ameren Illinois Company
Derivative [Line Items]
Derivative assets	96	41
Derivative Liability	65	125
Ameren Illinois Company | Fuel oils | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company | Fuel oils | Other assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company | Natural gas | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	59	28
Ameren Illinois Company | Natural gas | Other assets
Derivative [Line Items]
Derivative assets	27	13
Ameren Illinois Company | Natural gas | Other current liabilities
Derivative [Line Items]
Derivative Liability	7	6
Ameren Illinois Company | Natural gas | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	4	2
Ameren Illinois Company | Power | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	9	0
Ameren Illinois Company | Power | Other assets
Derivative [Line Items]
Derivative assets	1	0
Ameren Illinois Company | Power | Other current liabilities
Derivative [Line Items]
Derivative Liability	1	9
Ameren Illinois Company | Power | Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	53	108
Ameren Illinois Company | Uranium | Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company | Uranium | Other assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company | Uranium | Other current liabilities
Derivative [Line Items]
Derivative Liability	$ 0	$ 0

Derivative Financial Instrume_5

Derivative Financial Instruments (Offsetting Assets and Liabilities) (Details) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	$ 208	$ 90
Gross derivative instruments not offset in the balance sheet	52	19
Gross cash collateral received not offset in the balance sheet	30	0
Net derivative asset	126	71
Gross derivative liability amount recognized on the balance sheet	236	202
Gross derivative instruments not offset in the balance sheet	52	19
Gross cash collateral posted not offset in the balance sheet	127	47
Net derivative liability	57	136
Union Electric Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	112	49
Gross derivative instruments not offset in the balance sheet	36	15
Gross cash collateral received not offset in the balance sheet	15	0
Net derivative asset	61	34
Gross derivative liability amount recognized on the balance sheet	171	77
Gross derivative instruments not offset in the balance sheet	36	15
Gross cash collateral posted not offset in the balance sheet	127	47
Net derivative liability	8	15
Ameren Illinois Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	96	41
Gross derivative instruments not offset in the balance sheet	16	4
Gross cash collateral received not offset in the balance sheet	15	0
Net derivative asset	65	37
Gross derivative liability amount recognized on the balance sheet	65	125
Gross derivative instruments not offset in the balance sheet	16	4
Gross cash collateral posted not offset in the balance sheet	0	0
Net derivative liability	$ 49	$ 121

Derivative Financial Instrume_6

Derivative Financial Instruments (Credit Risk) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($)
Credit Derivatives [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	$ 172
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	108
Union Electric Company
Credit Derivatives [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	83
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	42
Ameren Illinois Company
Credit Derivatives [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	89
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 66

Derivative Financial Instrume_7

Derivative Financial Instruments (Derivative Instruments With Credit Risk-Related Contingent Features (Details) $ in Millions	Jun. 30, 2022 USD ($)
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	$ 88
Cash Collateral Posted	29
Potential Aggregate Amount of Additional Collateral Required	16
Union Electric Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	76
Cash Collateral Posted	29
Potential Aggregate Amount of Additional Collateral Required	12
Ameren Illinois Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	12
Cash Collateral Posted	0
Potential Aggregate Amount of Additional Collateral Required	$ 4

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	$ 950	$ 1,152
Assets fair value	1,158	1,242
Excluded receivables, payables, and accrued income, net	7	7
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	602	824
Assets fair value	656	848
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	348	328
Assets fair value	446	373
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	56	21
Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	208	90
Derivative Liability	236	202
Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	54	24
Derivative Liability	100	45
Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	98	45
Derivative Liability	10	7
Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	56	21
Derivative Liability	126	150
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	950	1,152
Assets fair value	1,062	1,201
Union Electric Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	602	824
Assets fair value	651	847
Union Electric Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	348	328
Assets fair value	375	340
Union Electric Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	36	14
Union Electric Company | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	112	49
Derivative Liability	171	77
Union Electric Company | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	49	23
Derivative Liability	100	45
Union Electric Company | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	27	12
Derivative Liability	4	2
Union Electric Company | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	36	14
Derivative Liability	67	30
Union Electric Company | Fuel oils | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	30	13
Union Electric Company | Fuel oils | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	27	13
Union Electric Company | Fuel oils | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Union Electric Company | Fuel oils | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	0
Union Electric Company | Natural gas | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	28	12
Derivative Liability	6	3
Union Electric Company | Natural gas | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	0
Derivative Liability	0	0
Union Electric Company | Natural gas | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	27	12
Derivative Liability	4	2
Union Electric Company | Natural gas | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	2	1
Union Electric Company | Power | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	50	23
Derivative Liability	165	73
Union Electric Company | Power | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	21	10
Derivative Liability	100	45
Union Electric Company | Power | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company | Power | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	29	13
Derivative Liability	65	28
Union Electric Company | Uranium | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	1
Derivative Liability	0	1
Union Electric Company | Uranium | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company | Uranium | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company | Uranium | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	1
Derivative Liability	0	1
Union Electric Company | Equity securities: | U.S. large capitalization
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	602	824
Union Electric Company | Equity securities: | U.S. large capitalization | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	602	824
Union Electric Company | Equity securities: | U.S. large capitalization | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Equity securities: | U.S. large capitalization | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | U.S. Treasury and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	173	141
Union Electric Company | Debt securities: | U.S. Treasury and agency securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | U.S. Treasury and agency securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	173	141
Union Electric Company | Debt securities: | U.S. Treasury and agency securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	121	131
Union Electric Company | Debt securities: | Corporate bonds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Corporate bonds | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	121	131
Union Electric Company | Debt securities: | Corporate bonds | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Other Debt Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	54	56
Union Electric Company | Debt securities: | Other Debt Securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company | Debt securities: | Other Debt Securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	54	56
Union Electric Company | Debt securities: | Other Debt Securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	96	41
Ameren Illinois Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	5	1
Ameren Illinois Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	71	33
Ameren Illinois Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	20	7
Ameren Illinois Company | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	65	125
Ameren Illinois Company | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	0	0
Ameren Illinois Company | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	6	5
Ameren Illinois Company | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	59	120
Ameren Illinois Company | Natural gas | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	86	41
Derivative Liability	11	8
Ameren Illinois Company | Natural gas | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	5	1
Derivative Liability	0	0
Ameren Illinois Company | Natural gas | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	71	33
Derivative Liability	6	5
Ameren Illinois Company | Natural gas | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	7
Derivative Liability	5	3
Ameren Illinois Company | Power | Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	0
Derivative Liability	54	117
Ameren Illinois Company | Power | Commodity Contract | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Ameren Illinois Company | Power | Commodity Contract | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Ameren Illinois Company | Power | Commodity Contract | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10	0
Derivative Liability	$ 54	$ 117

Fair Value Measurements (Sche_2

Fair Value Measurements (Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy) (Details) - Power - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (127)	$ (188)	$ (132)	$ (196)
Included in regulatory assets/liabilities	27	14	29	18
Settlements, assets	20	3	23	7
Change in unrealized gains (losses) related to assets/liabilities held at period end	32	13	36	21
Ending balance	(80)	(171)	(80)	(171)
Union Electric Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(53)	(3)	(15)	2
Included in regulatory assets/liabilities	(5)	(1)	(45)	(6)
Settlement, liabilities		(1)		(1)
Settlements, assets	22		24
Change in unrealized gains (losses) related to assets/liabilities held at period end	2	(2)	(36)	(3)
Ending balance	(36)	(5)	(36)	(5)
Ameren Illinois Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(74)	(185)	(117)	(198)
Included in regulatory assets/liabilities	32	15	74	24
Settlement, liabilities	(2)		(1)
Settlements, assets		4		8
Change in unrealized gains (losses) related to assets/liabilities held at period end	30	15	72	24
Ending balance	$ (44)	$ (166)	$ (44)	$ (166)

Fair Value Measurements (Sche_3

Fair Value Measurements (Schedule Of Valuation Process And Unobservable Inputs) (Details) - Power $ in Millions	Jun. 30, 2022 USD ($) $ / MMBTU $ / MWh	Dec. 31, 2021 USD ($) $ / MWh $ / MMBTU
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative assets | $	$ 39	$ 13
Derivative liabilities | $	$ (119)	$ (145)
Commodity Forward Price | Discounted cash flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	36	32
Commodity Forward Price | Discounted cash flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	122	55
Commodity Forward Price | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	65	40
Nodal Basis | Discounted cash flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(17)	(14)
Nodal Basis | Discounted cash flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	3	0
Nodal Basis | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(6)	(2)
Commodity Future Price | Discounted cash flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input | $ / MMBTU	0
Commodity Future Price | Discounted cash flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input | $ / MMBTU	3
Commodity Future Price | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input | $ / MMBTU	2	0

Fair Value Measurements (Sche_4

Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Financial Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	$ 161	$ 155	$ 267	$ 301
Short-term debt	1,021	545
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8	17	145
Short-term debt	285	165
Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133	$ 242	$ 147
Short-term debt	141	103
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	161	155
Investments in industrial development revenue bonds	248	248
Short-term debt	1,021	545
Long-term debt (including current portion)	13,590	13,067
Debt Issuance Costs, Net	97	94
Carrying Amount | Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments in industrial development revenue bonds	248	248
Short-term debt	285	165
Long-term debt (including current portion)	6,139	5,619
Debt Issuance Costs, Net	43	38
Carrying Amount | Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133
Short-term debt	141	103
Long-term debt (including current portion)	4,394	4,392
Debt Issuance Costs, Net	37	39
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	161	155
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	1,021	545
Long-term Debt, Fair Value	12,516	14,521
Fair Value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	161	155
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	1,021	545
Long-term Debt, Fair Value	12,016	13,930
Fair Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	500	591
Fair Value | Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	285	165
Long-term Debt, Fair Value	5,641	6,321
Fair Value | Union Electric Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Union Electric Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	285	165
Long-term Debt, Fair Value	5,641	6,321
Fair Value | Union Electric Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133
Short-term Debt, Fair Value	141	103
Long-term Debt, Fair Value	4,037	4,971
Fair Value | Ameren Illinois Company | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value | Ameren Illinois Company | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	141	103
Long-term Debt, Fair Value	4,037	4,971
Fair Value | Ameren Illinois Company | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	$ 0	$ 0

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Details) - Ameren Services Support Services Agreement - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Union Electric Company
Related Party Transaction [Line Items]
Due from Related Parties	$ 80	$ 77
Ameren Illinois Company
Related Party Transaction [Line Items]
Due from Related Parties	$ 83	$ 80

Related Party Transactions (Sch

Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Union Electric Company
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 37	$ 46
Accounts Receivable, Related Parties, Current	55	44
Union Electric Company | Income taxes payable to parent
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	0	0
Union Electric Company | Income taxes receivable from parent
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	45	27
Ameren Illinois Company
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	118	64
Accounts Receivable, Related Parties, Current	9	24
Ameren Illinois Company | Income taxes payable to parent
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	82	8
Ameren Illinois Company | Income taxes receivable from parent
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	$ 0	$ 18

Related Party Transactions (Eff

Related Party Transactions (Effects of Related-party Transactions on the Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Union Electric Company | Ameren Missouri Power Supply Agreements with Ameren Illinois
Related Party Transaction [Line Items]
Operating Revenues	$ 1	$ 3	$ 5	$ 5
Union Electric Company | Ameren Missouri and Ameren Illinois Rent and Facility Services
Related Party Transaction [Line Items]
Operating Revenues	6	7	12	14
Operating Expenses	1	1	1	1
Union Electric Company | Ameren Missouri and Ameren Illinois Miscellaneous Support Services
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Union Electric Company | Total Related Party Operating Revenues
Related Party Transaction [Line Items]
Operating Revenues	7	10	17	19
Union Electric Company | Ameren Missouri and Ameren Illinois Transmission Services from ATXI
Related Party Transaction [Line Items]
Operating Expenses	1	1	1	2
Union Electric Company | Purchased Power
Related Party Transaction [Line Items]
Operating Expenses	1	1	1	2
Union Electric Company | Ameren Services Support Services Agreement
Related Party Transaction [Line Items]
Operating Expenses	33	34	71	69
Union Electric Company | Total Related Party Other Operations and Maintenance
Related Party Transaction [Line Items]
Operating Expenses	33	34	71	69
Union Electric Company | Money pool borrowings (advances)
Related Party Transaction [Line Items]
Interest Charges (Income)	1	1	1	1
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Rent and Facility Services
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Operating Expenses	1	1	1	2
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Miscellaneous Support Services
Related Party Transaction [Line Items]
Operating Revenues	1	2	1	2
Ameren Illinois Company | Total Related Party Operating Revenues
Related Party Transaction [Line Items]
Operating Revenues	1	2	1	2
Ameren Illinois Company | Ameren Illinois Power Supply Agreements with Ameren Missouri
Related Party Transaction [Line Items]
Operating Expenses	1	3	5	5
Ameren Illinois Company | Ameren Missouri and Ameren Illinois Transmission Services from ATXI
Related Party Transaction [Line Items]
Operating Expenses	1	1	1	1
Ameren Illinois Company | Purchased Power
Related Party Transaction [Line Items]
Operating Expenses	1	4	5	6
Ameren Illinois Company | Ameren Services Support Services Agreement
Related Party Transaction [Line Items]
Operating Expenses	32	31	67	64
Ameren Illinois Company | Total Related Party Other Operations and Maintenance
Related Party Transaction [Line Items]
Operating Expenses	32	32	68	66
Ameren Illinois Company | Money pool borrowings (advances)
Related Party Transaction [Line Items]
Interest Charges (Income)	$ 1	$ 1	$ 1	$ 1

Commitments And Contingencies (

Commitments And Contingencies (Environmental Matters) (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) energyCenter scrubber site	Dec. 31, 2021 USD ($)
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 781	$ 764
Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	125
Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	$ 175
Union Electric Company
Loss Contingencies [Line Items]
Number of Energy Center Scrubbers | scrubber	2
Number of Months of System Support Agreement	12 months
Number of Energy Centers Constructing Wastewater Treatment Facilities | energyCenter	3
Number of energy centers | energyCenter	4
Number of Days to Comply after Final EPA Determination	135 days
Asset Retirement Obligation	$ 777	760
Number of Ameren Missouri Natural Gas Energy Centers Subject To IETL | energyCenter	4
Union Electric Company | Coal Fired Electric Generation Equipment
Loss Contingencies [Line Items]
Plant To Be Abandoned, Net	$ 600
Union Electric Company | Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	125
Union Electric Company | Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	175
Ameren Illinois Company
Loss Contingencies [Line Items]
Asset Retirement Obligation	4	$ 4
Coal Combustion Residuals Estimate | Union Electric Company | Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	60
Coal Combustion Residuals Estimate | Union Electric Company | Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	80
Manufactured Gas Plant
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 78
Manufactured Gas Plant | Ameren Illinois Company
Loss Contingencies [Line Items]
Number of remediation sites | site	44
Accrual for environmental loss contingencies	$ 78
Manufactured Gas Plant | Ameren Illinois Company | Minimum
Loss Contingencies [Line Items]
Estimate of possible loss	78
Manufactured Gas Plant | Ameren Illinois Company | Maximum
Loss Contingencies [Line Items]
Estimate of possible loss	147
Rush Island Energy Center | Union Electric Company
Loss Contingencies [Line Items]
Rate Base	500
New CCR Rules Estimate
Loss Contingencies [Line Items]
Asset Retirement Obligation	77
New CCR Rules Estimate | Union Electric Company
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 77

Callaway Energy Center (Insuran

Callaway Energy Center (Insurance Disclosure) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) yr
Nuclear Waste Matters [Line Items]
Decommissioning Cost	$ 7
Frequency of Decommissioning Cost Study	3 years
Proceeds from Insurance Settlement, Investing Activities	$ 22
Number Of Years The Limit Of Liability And The Maximum Potential Annual Payments Are Adjusted	5 years
Number Of Weeks Of Coverage After The First Twelve Weeks Of An Outage | yr	1
Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage | yr	1.365
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	$ 450
Insurance Maximum Coverage per Incident	0
Public Liability And Nuclear Worker Liability - Pool Participation
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	13,073
Insurance Maximum Coverage per Incident	138
Threshold Amount For Retrospective Insurance Assessment For Covered Loss Under Public Liability And Nuclear Worker Liability Insurance Policy	450
Maximum Annual Payment Per Incident At Licensed Commercial Nuclear Reactor	21
Public Liability
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	13,523
Insurance Maximum Coverage per Incident	138
Property Damage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	3,200
Insurance Maximum Coverage per Incident	26
Accidental Outage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	490
Insurance Maximum Coverage per Incident	7
Amount Of Weekly Indemnity Coverage Commencing Twelve Weeks After Power Outage	4.5
Amount Of Additional Weekly Indemnity Coverage Commencing After Initial Indemnity Coverage	3.6
Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit	490
Sub-Limit Of Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit For Non-Nuclear Events	328
Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	2,700
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	3,200
Non-Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	2,300
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	1,800
Property Damage European Mutual Association for Nuclear Insurance
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	$ 490

Retirement Benefits (Components

Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total non-service cost components	$ (47)	$ (34)	$ (93)	$ (68)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	31	34	64	67
Interest cost	41	38	81	76
Expected return on plan assets	(80)	(74)	(160)	(149)
Prior service benefit	0	0	0	0
Actuarial loss (gain)	6	20	12	37
Total non-service cost components	(33)	(16)	(67)	(36)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	(2)	18	(3)	31
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	5	6	10	12
Interest cost	9	8	17	16
Expected return on plan assets	(22)	(20)	(43)	(40)
Prior service benefit	(1)	(1)	(2)	(2)
Actuarial loss (gain)	(5)	(2)	(9)	(3)
Total non-service cost components	(19)	(15)	(37)	(29)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (14)	$ (9)	$ (27)	$ (17)

Retirement Benefits (Summary of

Retirement Benefits (Summary of Benefit Plan Costs Incurred) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ (2)	$ 18	$ (3)	$ 31
Pension Plan | Union Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(1)	9	(2)	15
Pension Plan | Ameren Illinois Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	0	9	1	17
Pension Plan | Other Affiliated Entities And Intercompany Eliminations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(1)	0	(2)	(1)
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(14)	(9)	(27)	(17)
Other Postretirement Benefit Plan, Defined Benefit | Union Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(4)	(1)	(7)	(2)
Other Postretirement Benefit Plan, Defined Benefit | Ameren Illinois Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(10)	(8)	(20)	(15)
Other Postretirement Benefit Plan, Defined Benefit | Other Affiliated Entities And Intercompany Eliminations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ 0	$ 0	$ 0	$ 0

Income Taxes (Schedule of Effec

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21%	21%	21%	21%
Increases (decreases) from:
Amortization of deferred investment tax credit	0%	0%	0%	0%
Amortization of excess deferred taxes	(8.00%)	(9.00%)	(8.00%)	(9.00%)
Depreciation differences	0%	0%	0%	0%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	1%	0%
Renewable and other tax credits	(4.00%)	(4.00%)	(5.00%)	(5.00%)
State tax	5%	5%	5%	5%
Effective income tax rate	15%	13%	13%	12%
Union Electric Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21%	21%	21%	21%
Increases (decreases) from:
Amortization of deferred investment tax credit	(1.00%)	(1.00%)	(1.00%)	(1.00%)
Amortization of excess deferred taxes	(15.00%)	(17.00%)	(16.00%)	(17.00%)
Depreciation differences	0%	1%	0%	1%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	0%	0%
Renewable and other tax credits	(10.00%)	(10.00%)	(10.00%)	(10.00%)
State tax	3%	3%	3%	3%
Effective income tax rate	(2.00%)	(3.00%)	(3.00%)	(3.00%)
Ameren Illinois Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21%	21%	21%	21%
Increases (decreases) from:
Amortization of deferred investment tax credit	0%	0%	0%	0%
Amortization of excess deferred taxes	(2.00%)	(2.00%)	(2.00%)	(3.00%)
Depreciation differences	(1.00%)	1%	0%	0%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	0%	0%
Renewable and other tax credits	0%	(1.00%)	0%	0%
State tax	7%	7%	7%	7%
Effective income tax rate	25%	26%	26%	25%

Supplemental Information (Cash

Supplemental Information (Cash and Cash Equivalents) (Details) - USD ($)	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	$ 7,000,000	$ 8,000,000
Restricted cash included in “Other current assets”	7,000,000	16,000,000
Restricted cash included in “Other assets”	142,000,000	127,000,000
Restricted cash included in “Nuclear decommissioning trust fund”	5,000,000	4,000,000
Total cash, cash equivalents, and restricted cash	161,000,000	155,000,000	$ 267,000,000	$ 301,000,000
Union Electric Company
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	0	0
Restricted cash included in “Other current assets”	2,000,000	4,000,000
Restricted cash included in “Other assets”	0	0
Restricted cash included in “Nuclear decommissioning trust fund”	5,000,000	4,000,000
Total cash, cash equivalents, and restricted cash	7,000,000	8,000,000	17,000,000	145,000,000
Ameren Illinois Company
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	0	0
Restricted cash included in “Other current assets”	4,000,000	6,000,000
Restricted cash included in “Other assets”	142,000,000	127,000,000
Restricted cash included in “Nuclear decommissioning trust fund”	0	0
Total cash, cash equivalents, and restricted cash	$ 146,000,000	$ 133,000,000	$ 242,000,000	$ 147,000,000

Supplemental Information (Allow

Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	$ 28	$ 47	$ 29	$ 50
Bad debt expense	7	(3)	11	1
Net write-offs	(5)	(2)	(10)	(9)
End of period	30	42	30	42
Payables for purchased receivables	32		32		$ 27
Union Electric Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	11	15	13	16
Bad debt expense	2	2	3	3
Net write-offs	(1)	(1)	(4)	(3)
End of period	12	16	12	16
Ameren Illinois Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	17	32	16	34
Bad debt expense	5	(5)	8	(2)
Net write-offs	(4)	(1)	(6)	(6)
End of period	18	$ 26	18	$ 26
Payables for purchased receivables	$ 32		$ 32		$ 27

Supplemental Information (Suppl

Supplemental Information (Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Supplemental Cash Flow Information [Line Items]
Wind generation expenditures	$ 224		$ 417
Accrued capital expenditures		$ 408	434
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund		(211)	85
Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		31	33
Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		8	0
Union Electric Company
Supplemental Cash Flow Information [Line Items]
Wind generation expenditures	$ 224		417
Accrued capital expenditures		204	259
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund		(211)	85
Union Electric Company | Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0
Union Electric Company | Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0
Ameren Illinois Company
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures		193	174
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund		0	0
Ameren Illinois Company | Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0
Ameren Illinois Company | Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		$ 0	$ 0

Supplemental Information (Sched

Supplemental Information (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	$ 764
Accretion	15
Change in estimates	2
Asset Retirement Obligation, Ending Balance	781
Other current liabilities	824	$ 568
Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	760
Accretion	15
Change in estimates	2
Asset Retirement Obligation, Ending Balance	777
Other current liabilities	134	116
Ameren Illinois Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	4
Accretion	0
Change in estimates	0
Asset Retirement Obligation, Ending Balance	4
Other current liabilities	277	251
Asset Retirement Obligation Balance
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	7	7
Asset Retirement Obligation Balance | Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	$ 7	$ 7

Supplemental Information (Narra

Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Available for Grant	8,800,000
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	$ 5	$ 5
Deferred Compensation Liability, Classified, Noncurrent	$ 89		$ 91
Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Performance Shares | Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	267,849
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 25
Stock Issued During Period Percentage Conversion Of Units, Low End	0%
Stock Issued During Period Percentage Conversion Of Units, High End	200%
Performance Shares | Market performance measures achievement | Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	229,566
Performance Shares | Renewable generation and energy storage installation targets | Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	38,283
Restricted Stock Units (RSUs) | Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	122,882
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 11

Supplemental Information (Sch_2

Supplemental Information (Schedule Of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accounting Policies [Line Items]
Excise tax expense	$ 67	$ 62	$ 146	$ 132
Union Electric Company
Accounting Policies [Line Items]
Excise tax expense	39	35	73	66
Ameren Illinois Company
Accounting Policies [Line Items]
Excise tax expense	$ 28	$ 27	$ 73	$ 66

Supplemental Information (Earni

Supplemental Information (Earnings Per Share) (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share Reconciliation [Abstract]
Weighted-average Common Shares Outstanding – Basic	258,200,000	256,100,000	258,000,000	255,200,000
Assumed settlement of performance share units and restricted stock units	1,000,000	1,100,000	1,100,000	1,300,000
Dilutive effect of forward sale agreements	200,000	0	100,000	0
Weighted-average Common Shares Outstanding – Diluted	259,400,000	257,200,000	259,200,000	256,500,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)			0	0

Segment Information (Schedule O

Segment Information (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 1,726	$ 1,472	$ 3,605	$ 3,038
Net income (loss) attributable to common shareholders	207	207	459	440
Capital expenditures	764	876	1,538	1,763
Wind generation expenditures		224		417
Union Electric Company
Segment Reporting Information [Line Items]
Revenues	919	809	1,737	1,513
Net income (loss) attributable to common shareholders	100	111	150	158
Wind generation expenditures		224		417
Ameren Illinois Company
Segment Reporting Information [Line Items]
Revenues	769	629	1,793	1,452
Net income (loss) attributable to common shareholders	103	86	272	235
Capital expenditures	357	309	699	646
Operating Segments | Union Electric Company
Segment Reporting Information [Line Items]
Revenues	912	799	1,720	1,494
Net income (loss) attributable to common shareholders	100	111	150	158
Capital expenditures	392	567	806	1,101
Operating Segments | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Revenues	504	386	968	797
Net income (loss) attributable to common shareholders	51	41	100	87
Capital expenditures	143	129	281	286
Operating Segments | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Revenues	184	168	665	515
Net income (loss) attributable to common shareholders	6	8	86	83
Capital expenditures	69	61	118	109
Operating Segments | Ameren Transmission
Segment Reporting Information [Line Items]
Revenues	126	119	252	232
Net income (loss) attributable to common shareholders	63	55	121	102
Capital expenditures	160	131	332	272
Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Revenues	504	388	969	799
Net income (loss) attributable to common shareholders	51	41	100	87
Capital expenditures	143	129	281	286
Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Revenues	184	168	665	515
Net income (loss) attributable to common shareholders	6	8	86	83
Capital expenditures	69	61	118	109
Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Revenues	81	73	159	138
Net income (loss) attributable to common shareholders	46	37	86	65
Capital expenditures	145	119	300	251
Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment revenues	(31)	(29)	(62)	(55)
Capital expenditures	(1)	(12)	(2)	(6)
Intersegment Eliminations | Union Electric Company
Segment Reporting Information [Line Items]
Intersegment revenues	(7)	(10)	(17)	(19)
Intersegment Eliminations | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	(2)	(1)	(2)
Intersegment Eliminations | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations | Ameren Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	(24)	(17)	(44)	(34)
Intersegment Eliminations | Ameren Illinois Company
Segment Reporting Information [Line Items]
Intersegment revenues	(24)	(15)	(44)	(31)
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	(24)	(15)	(44)	(31)
Other
Segment Reporting Information [Line Items]
Net income (loss) attributable to common shareholders	(13)	$ (8)	2	10
Capital expenditures	$ 1		$ 3	$ 1

Segment Information (Disaggrega

Segment Information (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 1,726	$ 1,472	$ 3,605	$ 3,038
Revenues	1,726	1,472	3,605	3,038
Revenues from alternative revenue programs	40	36	85	89
Other revenues not from contracts with customers	(34)	67	(31)	69
Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	0	(5)	(6)	(15)
Other revenues not from contracts with customers	(36)	66	(36)	64
Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	41	34	96	95
Other revenues not from contracts with customers	1	0	3	3
Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	3	2	(2)	5
Other revenues not from contracts with customers	1	1	2	2
Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(4)	5	(3)	4
Other revenues not from contracts with customers	0	0	0	0
Electric
Disaggregation of Revenue [Line Items]
Revenues	1,513	1,284	2,831	2,440
Revenues	1,513	1,284	2,831	2,440
Electric | Residential
Disaggregation of Revenue [Line Items]
Revenues	655	546	1,250	1,087
Electric | Commercial
Disaggregation of Revenue [Line Items]
Revenues	478	398	876	746
Electric | Industrial
Disaggregation of Revenue [Line Items]
Revenues	126	105	228	191
Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	254	235	477	416
Natural gas
Disaggregation of Revenue [Line Items]
Revenues	213	188	774	598
Revenues	213	188	774	598
Natural gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	133	123	553	408
Natural gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	38	33	157	112
Natural gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	12	4	31	19
Natural gas | Other
Disaggregation of Revenue [Line Items]
Revenues	30	28	33	59
Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Revenues	769	629	1,793	1,452
Revenues	769	629	1,793	1,452
Revenues from alternative revenue programs	41	38	92	101
Other revenues not from contracts with customers	2	1	5	5
Ameren Illinois Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	401	330	1,033	810
Ameren Illinois Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	210	156	465	352
Ameren Illinois Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	64	37	126	85
Ameren Illinois Company | Other
Disaggregation of Revenue [Line Items]
Revenues	94	106	169	205
Ameren Illinois Company | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	41	34	96	95
Other revenues not from contracts with customers	1	0	3	3
Ameren Illinois Company | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	3	2	(2)	5
Other revenues not from contracts with customers	1	1	2	2
Ameren Illinois Company | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(3)	2	(2)	1
Other revenues not from contracts with customers	0	0	0	0
Ameren Illinois Company | Electric
Disaggregation of Revenue [Line Items]
Revenues	585	461	1,128	937
Ameren Illinois Company | Natural gas
Disaggregation of Revenue [Line Items]
Revenues	184	168	665	515
Operating Segments | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	912	799	1,720	1,494
Revenues	919	809	1,737	1,513
Operating Segments | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	504	386	968	797
Revenues	504	388	969	799
Operating Segments | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	184	168	665	515
Revenues	184	168	665	515
Operating Segments | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	126	119	252	232
Revenues	150	136	296	266
Operating Segments | Electric | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	890	789	1,628	1,430
Operating Segments | Electric | Union Electric Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	371	328	703	640
Operating Segments | Electric | Union Electric Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	298	271	538	487
Operating Segments | Electric | Union Electric Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	73	71	130	123
Operating Segments | Electric | Union Electric Company | Other
Disaggregation of Revenue [Line Items]
Revenues	148	119	257	180
Operating Segments | Electric | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	504	388	969	799
Operating Segments | Electric | Ameren Illinois Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenues	284	218	547	447
Operating Segments | Electric | Ameren Illinois Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenues	180	127	338	259
Operating Segments | Electric | Ameren Illinois Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenues	53	34	98	68
Operating Segments | Electric | Ameren Illinois Electric Distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	(13)	9	(14)	25
Operating Segments | Electric | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Illinois Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	150	136	296	266
Operating Segments | Electric | Ameren Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Electric | Ameren Transmission | Other
Disaggregation of Revenue [Line Items]
Revenues	150	136	296	266
Operating Segments | Natural gas | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	29	20	109	83
Operating Segments | Natural gas | Union Electric Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	16	11	67	45
Operating Segments | Natural gas | Union Electric Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	8	4	30	19
Operating Segments | Natural gas | Union Electric Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	1	1	3	2
Operating Segments | Natural gas | Union Electric Company | Other
Disaggregation of Revenue [Line Items]
Revenues	4	4	9	17
Operating Segments | Natural gas | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	184	168	665	515
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	117	112	486	363
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	30	29	127	93
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	11	3	28	17
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	26	24	24	42
Operating Segments | Natural gas | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Natural gas | Ameren Transmission | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	504	388	969	799
Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	184	168	665	515
Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	81	73	159	138
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	504	388	969	799
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenues	284	218	547	447
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenues	180	127	338	259
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenues	53	34	98	68
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	(13)	9	(14)	25
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	105	88	203	169
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Other
Disaggregation of Revenue [Line Items]
Revenues	105	88	203	169
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	184	168	665	515
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	117	112	486	363
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	30	29	127	93
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	11	3	28	17
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	26	24	24	42
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(31)	(29)	(62)	(55)
Revenues	(31)	(29)	(62)	(55)
Intersegment Eliminations | Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	(7)	(10)	(17)	(19)
Intersegment Eliminations | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	(2)	(1)	(2)
Intersegment Eliminations | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	(24)	(17)	(44)	(34)
Intersegment Eliminations | Electric
Disaggregation of Revenue [Line Items]
Revenues	(31)	(29)	(62)	(55)
Intersegment Eliminations | Electric | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Electric | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Electric | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	(31)	(29)	(62)	(55)
Intersegment Eliminations | Natural gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Natural gas | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Natural gas | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Natural gas | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Natural gas | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Revenues	(24)	(15)	(44)	(31)
Revenues	(24)	(15)	(44)	(31)
Intersegment Eliminations | Ameren Illinois Company | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company | Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company | Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company | Other
Disaggregation of Revenue [Line Items]
Revenues	(24)	(15)	(44)	(31)
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	$ (24)	$ (15)	$ (44)	$ (31)