Consolidated Statement Of Income (Loss) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Revenues:
Operating revenues	$ 5,910	$ 6,291	$ 6,174
Operating Expenses:
Fuel	535	769	737
Purchased Power	556	581	638
Natural gas purchased for resale	331	374	311
Other operations and maintenance	1,745	1,772	1,705
Depreciation and Amortization	995	955	896
Taxes other than income taxes	481	483	477
Total operating expenses	4,643	4,934	4,764
Operating Income	1,267	1,357	1,410
Other Income, Net	130	102	86
Interest charges	381	401	391
Income Before Income Taxes	1,016	1,058	1,105
Income taxes	182	237	576
Net Income	834	821	529
Net Income Attributable to Noncontrolling Interest	6	6	6
Net Income (Loss) Available to Common Stockholders, Basic	828	815	523
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	5	(4)	5
Comprehensive Income	839	817	534
Comprehensive Income Attributable to Noncontrolling Interests	6	6	6
Comprehensive Income Attributable to Ameren Common Shareholders	$ 833	$ 811	$ 528
Earnings per Common Share – Basic:
Earnings per Common Share – Basic (in dollars per share)	$ 3.37	$ 3.34	$ 2.16
Earnings per Common Share – Diluted:
Earnings per Common Share – Diluted (in dollars per share)	$ 3.35	$ 3.32	$ 2.14
Weighted-average Common Shares Outstanding - Basic (in shares)	245.6	243.8	242.6
Weighted-average Common Shares Outstanding - Diluted (in shares)	247.1	245.8	244.2
Union Electric Company
Operating Revenues:
Operating revenues	$ 3,243	$ 3,589	$ 3,537
Operating Expenses:
Fuel	535	769	737
Purchased Power	193	164	245
Natural gas purchased for resale	53	56	47
Other operations and maintenance	960	972	925
Depreciation and Amortization	556	550	533
Taxes other than income taxes	329	329	328
Total operating expenses	2,626	2,840	2,815
Operating Income	617	749	722
Other Income, Net	58	56	65
Interest charges	178	200	207
Income Before Income Taxes	497	605	580
Income taxes	68	124	254
Net Income	429	481	326
Preferred Stock Dividends	3	3	3
Net Income Available to Common Shareholder	426	478	323
Ameren Illinois Company
Operating Revenues:
Operating revenues	2,527	2,576	2,527
Operating Expenses:
Purchased Power	368	429	417
Natural gas purchased for resale	278	318	264
Other operations and maintenance	782	799	799
Depreciation and Amortization	406	374	341
Taxes other than income taxes	143	144	137
Total operating expenses	1,977	2,064	1,958
Operating Income	550	512	569
Other Income, Net	53	42	12
Interest charges	147	149	144
Income Before Income Taxes	456	405	437
Income taxes	110	98	166
Net Income	346	307	271
Preferred Stock Dividends	3	3	3
Net Income Available to Common Shareholder	343	304	268
Electricity
Operating Revenues:
Operating revenues	4,981	5,339	5,307
Electricity | Union Electric Company
Operating Revenues:
Operating revenues	3,109	3,451	3,411
Electricity | Ameren Illinois Company
Operating Revenues:
Operating revenues	1,730	1,761	1,784
Natural gas
Operating Revenues:
Operating revenues	929	952	867
Natural gas | Union Electric Company
Operating Revenues:
Operating revenues	134	138	126
Natural gas | Ameren Illinois Company
Operating Revenues:
Operating revenues	$ 797	$ 815	$ 743