Consolidated Statement Of Income (Loss) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Revenues:
Operating revenues	$ 6,394	$ 5,794	$ 5,910
Operating Expenses:
Fuel	581	490	535
Purchased power	606	513	556
Natural gas purchased for resale	442	272	331
Other operations and maintenance	1,774	1,661	1,745
Depreciation and amortization	1,146	1,075	995
Taxes other than income taxes	512	483	481
Total operating expenses	5,061	4,494	4,643
Operating Income	1,333	1,300	1,267
Other Income, Net	202	151	130
Interest Charges	383	419	381
Income Before Income Taxes	1,152	1,032	1,016
Income Taxes	157	155	182
Net Income	995	877	834
Less: Net Income Attributable to Noncontrolling Interests	5	6	6
Net Income Attributable to Ameren Common Shareholders	990	871	828
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	14	16	5
Comprehensive Income	1,009	893	839
Less: Comprehensive Income Attributable to Noncontrolling Interests	5	6	6
Comprehensive Income Attributable to Ameren Common Shareholders	$ 1,004	$ 887	$ 833
Earnings per Common Share – Basic
Earnings per Common Share – Basic	$ 3.86	$ 3.53	$ 3.37
Earnings per Common Share – Diluted
Earnings per Common Share – Diluted	$ 3.84	$ 3.50	$ 3.35
Weighted-average Common Shares Outstanding – Basic	256.3	247.0	245.6
Weighted-average Common Shares Outstanding – Diluted	257.6	248.7	247.1
Union Electric Company
Operating Revenues:
Operating revenues	$ 3,353	$ 3,109	$ 3,243
Operating Expenses:
Fuel	581	490	535
Purchased power	227	171	193
Natural gas purchased for resale	60	43	53
Other operations and maintenance	948	886	960
Depreciation and amortization	632	604	556
Taxes other than income taxes	343	328	329
Total operating expenses	2,791	2,522	2,626
Operating Income	562	587	617
Other Income, Net	99	76	58
Interest Charges	137	190	178
Income Before Income Taxes	524	473	497
Income Taxes	3	34	68
Net Income	521	439	429
Preferred Stock Dividends	3	3	3
Net Income Attributable to Ameren Common Shareholders	518	436	426
Ameren Illinois Company
Operating Revenues:
Operating revenues	2,895	2,535	2,527
Operating Expenses:
Purchased power	400	355	368
Natural gas purchased for resale	382	229	278
Other operations and maintenance	820	775	782
Depreciation and amortization	472	434	406
Taxes other than income taxes	153	140	143
Total operating expenses	2,227	1,933	1,977
Operating Income	668	602	550
Other Income, Net	66	59	53
Interest Charges	164	155	147
Income Before Income Taxes	570	506	456
Income Taxes	143	124	110
Net Income	427	382	346
Preferred Stock Dividends	2	3	3
Net Income Attributable to Ameren Common Shareholders	425	379	343
Electric
Operating Revenues:
Operating revenues	5,297	4,911	4,981
Electric | Union Electric Company
Operating Revenues:
Operating revenues	3,212	2,984	3,109
Electric | Ameren Illinois Company
Operating Revenues:
Operating revenues	1,938	1,775	1,730
Natural gas
Operating Revenues:
Operating revenues	1,097	883	929
Natural gas | Union Electric Company
Operating Revenues:
Operating revenues	141	125	134
Natural gas | Ameren Illinois Company
Operating Revenues:
Operating revenues	$ 957	$ 760	$ 797