Consolidated Statement of Income (Loss) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating Revenues:
Electric		$ 1,700	$ 1,523	$ 4,093	$ 3,864
Gas		133	147	697	819
Total operating revenues		1,833	1,670	4,790	4,683
Operating Expenses:
Fuel		259	236	670	638
Purchased power		153	114	393	340
Gas purchased for resale		38	49	320	432
Other operations and maintenance		428	402	1,256	1,231
Provision for Callaway construction and operating license		0	0	69	0
Depreciation and amortization		201	187	594	551
Taxes other than income taxes		128	121	369	362
Total operating expenses		1,207	1,109	3,671	3,554
Operating Income		626	561	1,119	1,129
Other Income and Expenses:
Miscellaneous income	[1]	19	21	54	60
Miscellaneous expense	[1]	5	7	22	20
Total other income (expense)		14	14	32	40
Interest Charges		87	85	264	266
Income Before Income Taxes		553	490	887	903
Income Taxes		208	194	333	357
Income from Continuing Operations		345	296	554	546
Income (Loss) from Discontinued Operations, Net of Taxes (Note 12)		0	(1)	52	(3)
Net Income (Loss)		345	295	606	543
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		0	0	4	3
Comprehensive Income		343	293	605	541
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
Net Income from Continuing Operations Attributable to Noncontrolling Interests		2	2	5	5
Net Income (Loss):
Continuing Operations		343	294	549	541
Discontinued Operations		0	(1)	52	(3)
Net Income (Loss)		$ 343	$ 293	$ 601	$ 538
Earnings Per Share, Basic [Abstract]
Continuing Operations		$ 1.42	$ 1.21	$ 2.27	$ 2.23
Discontinued Operations		0.00	0.00	0.21	(0.01)
Earnings Per Share, Basic		1.42	1.21	2.48	2.22
Earnings Per Share, Diluted [Abstract]
Continuing Operations		1.41	1.20	2.26	2.21
Discontinued Operations		0.00	0.00	0.21	(0.01)
Earnings Per Share, Diluted		1.41	1.20	2.47	2.20
Dividends per Common Share		$ 0.41	$ 0.40	$ 1.23	$ 1.20
Average Common Shares Outstanding - Basic		242.6	242.6	242.6	242.6
Average Common Shares Outstanding - Diluted		243.9	244.3	243.8	244.3
Union Electric Company
Operating Revenues:
Electric		$ 1,151	$ 1,076	$ 2,752	$ 2,696
Gas		19	21	101	117
Other Revenue, Net		1		2	1
Total operating revenues		1,171	1,097	2,855	2,814
Operating Expenses:
Fuel		259	236	670	638
Purchased power		29	27	87	91
Gas purchased for resale		5	7	43	58
Other operations and maintenance		233	226	673	672
Provision for Callaway construction and operating license		0	0	69	0
Depreciation and amortization		125	118	367	351
Taxes other than income taxes		97	89	262	248
Total operating expenses		748	703	2,171	2,058
Operating Income		423	394	684	756
Other Income and Expenses:
Miscellaneous income		14	15	37	45
Miscellaneous expense		3	4	8	10
Total other income (expense)		11	11	29	35
Interest Charges		54	53	164	159
Income Before Income Taxes		380	352	549	632
Income Taxes		140	129	205	234
Net Income (Loss)		240	223	344	398
Other Comprehensive Income		0	0	0	0
Comprehensive Income		240	223	344	398
Net Income (Loss):
Net Income (Loss)		240	223	344	398
Earnings Per Share, Diluted [Abstract]
Preferred Stock Dividends		1	1	3	3
Net Income Available to Common Stockholder		239	222	341	395
Ameren Illinois Company
Operating Revenues:
Electric		540	445	1,316	1,162
Gas		115	127	597	703
Total operating revenues		655	572	1,913	1,865
Operating Expenses:
Purchased power		128	89	317	256
Gas purchased for resale		33	43	277	374
Other operations and maintenance		202	185	606	580
Depreciation and amortization		74	66	220	193
Taxes other than income taxes		29	31	101	109
Total operating expenses		466	414	1,521	1,512
Operating Income		189	158	392	353
Other Income and Expenses:
Miscellaneous income		4	4	15	12
Miscellaneous expense		3	2	10	7
Total other income (expense)		1	2	5	5
Interest Charges		33	31	99	90
Income Before Income Taxes		157	129	298	268
Income Taxes		59	54	114	110
Net Income (Loss)		98	75	184	158
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		0	0	(2)	(2)
Comprehensive Income		98	75	182	156
Net Income (Loss):
Net Income (Loss)		98	75	184	158
Earnings Per Share, Diluted [Abstract]
Preferred Stock Dividends				2	2
Net Income Available to Common Stockholder		$ 98	$ 75	$ 182	$ 156

[1] Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.