Consolidated Statement Of Income (Loss) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Revenues:
Electric	$ 5,310	$ 5,196	$ 5,180
Natural Gas	867	880	918
Total operating revenues	6,177	6,076	6,098
Operating Expenses:
Fuel	737	745	878
Purchased power	638	621	514
Natural gas purchased for resale	311	341	415
Other operations and maintenance	1,660	1,676	1,694
Provision for Callaway construction and operating license	0	0	69
Depreciation and amortization	896	845	796
Taxes other than income taxes	477	467	473
Total operating expenses	4,719	4,695	4,839
Operating Income	1,458	1,381	1,259
Other Income and Expenses:
Miscellaneous income	59	74	74
Miscellaneous expense	21	32	30
Total other income (expense)	38	42	44
Interest charges	391	382	355
Income Before Income Taxes	1,105	1,041	948
Income taxes	576	382	363
Income from Continuing Operations	529	659	585
Income from Discontinued Operations, Net of Tax	0	0	51
Net Income	529	659	636
Pension and other postretirement activity, net of income taxes (benefit)	5	(20)	6
Comprehensive Income	528	633	636
Less: Net Income Attributable to Noncontrolling Interests:
Continuing Operations	6	6	6
Net Income:
Net income attributable to Ameren Corporation - continuing operations	523	653	579
Discontinued Operations	0	0	51
Net income attributable to Ameren common shareholders	$ 523	$ 653	$ 630
Earnings per Common Share – Basic:
Continuing Operations - Basic (in dollars per share)	$ 2.16	$ 2.69	$ 2.39
Discontinued Operations - Basic (in dollars per share)	0.00	0.00	0.21
Earnings per Common Share – Basic (in dollars per share)	2.16	2.69	2.60
Earnings per Common Share – Diluted:
Continuing Operations - Diluted (in dollars per share)	2.14	2.68	2.38
Discontinued Operations - Diluted (in dollars per share)	0.00	0.00	0.21
Earnings per Common Share – Diluted (in dollars per share)	2.14	2.68	2.59
Dividends per Common Share (in dollars per share)	$ 1.778	$ 1.715	$ 1.655
Average Common Shares Outstanding - Basic (in shares)	242.6	242.6	242.6
Average Common Shares Outstanding - Diluted (in shares)	244.2	243.4	243.6
Union Electric Company
Operating Revenues:
Electric	$ 3,413	$ 3,394	$ 3,470
Natural Gas	126	128	137
Other	0	1	2
Total operating revenues	3,539	3,523	3,609
Operating Expenses:
Fuel	737	745	878
Purchased power	245	252	111
Natural gas purchased for resale	47	49	57
Other operations and maintenance	902	893	925
Provision for Callaway construction and operating license	0	0	69
Depreciation and amortization	533	514	492
Taxes other than income taxes	328	325	335
Total operating expenses	2,792	2,778	2,867
Operating Income	747	745	742
Other Income and Expenses:
Miscellaneous income	48	52	52
Miscellaneous expense	8	10	11
Total other income (expense)	40	42	41
Interest charges	207	211	219
Income Before Income Taxes	580	576	564
Income taxes	254	216	209
Net Income	326	360	355
Other Comprehensive Income	0	0	0
Comprehensive Income	326	360	355
Net Income:
Preferred Stock Dividends	3	3	3
Net Income Available to Common Stockholder	323	357	352
Ameren Illinois Company
Operating Revenues:
Electric	1,784	1,736	1,683
Natural Gas	743	754	783
Other	1	0	0
Total operating revenues	2,528	2,490	2,466
Operating Expenses:
Purchased power	417	399	420
Natural gas purchased for resale	264	292	358
Other operations and maintenance	789	804	797
Depreciation and amortization	341	319	295
Taxes other than income taxes	137	132	130
Total operating expenses	1,948	1,946	2,000
Operating Income	580	544	466
Other Income and Expenses:
Miscellaneous income	11	21	21
Miscellaneous expense	10	12	12
Total other income (expense)	1	9	9
Interest charges	144	140	131
Income Before Income Taxes	437	413	344
Income taxes	166	158	127
Net Income	271	255	217
Pension and other postretirement activity, net of income taxes (benefit)	0	(5)	(3)
Comprehensive Income	271	250	214
Net Income:
Preferred Stock Dividends	3	3	3
Net Income Available to Common Stockholder	$ 268	$ 252	$ 214