Consolidated Statement Of Income (Loss) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	$ 6,291	$ 6,174	$ 6,076
Operating Expenses:
Fuel	769	737	745
Purchased Power	581	638	623
Natural gas purchased for resale	374	311	341
Other operations and maintenance	1,772	1,705	1,733
Depreciation and amortization	955	896	845
Taxes other than income taxes	483	477	467
Total operating expenses	4,934	4,764	4,754
Operating Income	1,357	1,410	1,322
Other Nonoperating Income (Expense)	102	86	101
Interest charges	401	391	382
Income Before Income Taxes	1,058	1,105	1,041
Income taxes	237	576	382
Net Income	821	529	659
Net Income (Loss) Attributable to Noncontrolling Interest	6	6	6
Net Income (Loss) Available to Common Stockholders, Basic	815	523	653
Pension and other postretirement activity, net of income taxes (benefit)	(4)	5	(20)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	817	534	639
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	6	6	6
Comprehensive Income	$ 811	$ 528	$ 633
Earnings per Common Share – Basic:
Earnings per Common Share – Basic (in dollars per share)	$ 3.34	$ 2.16	$ 2.69
Earnings per Common Share – Diluted:
Earnings per Common Share – Diluted (in dollars per share)	$ 3.32	$ 2.14	$ 2.68
Average Common Shares Outstanding - Basic (in shares)	243.8	242.6	242.6
Average Common Shares Outstanding - Diluted (in shares)	245.8	244.2	243.4
Union Electric Company
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	$ 3,589	$ 3,537	$ 3,524
Operating Expenses:
Fuel	769	737	745
Purchased Power	164	245	254
Natural gas purchased for resale	56	47	49
Other operations and maintenance	972	925	912
Depreciation and amortization	550	533	514
Taxes other than income taxes	329	328	325
Total operating expenses	2,840	2,815	2,799
Operating Income	749	722	725
Other Nonoperating Income (Expense)	56	65	62
Interest charges	200	207	211
Income Before Income Taxes	605	580	576
Income taxes	124	254	216
Net Income	481	326	360
Preferred Stock Dividends	3	3	3
Earnings per Common Share – Diluted:
Net Income (Loss) Attributable to Parent	478	323	357
Ameren Illinois Company
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	2,576	2,527	2,489
Operating Expenses:
Purchased Power	429	417	399
Natural gas purchased for resale	318	264	292
Other operations and maintenance	799	799	828
Depreciation and amortization	374	341	319
Taxes other than income taxes	144	137	132
Total operating expenses	2,064	1,958	1,970
Operating Income	512	569	519
Other Nonoperating Income (Expense)	42	12	34
Interest charges	149	144	140
Income Before Income Taxes	405	437	413
Income taxes	98	166	158
Net Income	307	271	255
Pension and other postretirement activity, net of income taxes (benefit)	0	0	(5)
Comprehensive Income	307	271	250
Preferred Stock Dividends	3	3	3
Earnings per Common Share – Diluted:
Net Income (Loss) Attributable to Parent	304	268	252
Electricity
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	5,339	5,307	5,196
Electricity | Union Electric Company
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	3,451	3,411	3,396
Electricity | Ameren Illinois Company
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	1,761	1,784	1,735
Natural gas
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	952	867	880
Natural gas | Union Electric Company
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	138	126	128
Natural gas | Ameren Illinois Company
Operating Revenues:
Revenue from Contract with Customer, Including Assessed Tax	$ 815	$ 743	$ 754