Consolidated Statement of Income (Loss) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating Revenues:
Electric		$ 1,725	$ 1,700	$ 4,101	$ 4,093
Gas		134	133	619	697
Total operating revenues		1,859	1,833	4,720	4,790
Operating Expenses:
Fuel		205	259	574	670
Purchased power		178	153	451	393
Gas purchased for resale		34	38	227	320
Other operations and maintenance		411	428	1,246	1,256
Provision for Callaway construction and operating license		0	0	0	69
Depreciation and amortization		211	201	628	594
Taxes other than income taxes		129	128	358	369
Total operating expenses		1,168	1,207	3,484	3,671
Operating Income		691	626	1,236	1,119
Other Income and Expenses:
Miscellaneous income	[1]	18	19	54	54
Miscellaneous expense	[1]	8	5	21	22
Total other income (expense)		10	14	33	32
Interest Charges		97	87	287	264
Income Before Income Taxes		604	553	982	887
Income Taxes		233	208	356	333
Income from Continuing Operations		371	345	626	554
Income from Discontinued Operations, Net of Taxes		0	0	0	52
Net Income (Loss)		371	345	626	606
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		(1)	0	1	4
Comprehensive Income		368	343	622	605
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		369	343	621	549
Discontinued Operations		0	0	0	52
Net Income (Loss)		$ 369	$ 343	$ 621	$ 601
Earnings Per Share, Basic [Abstract]
Continuing Operations		$ 1.52	$ 1.42	$ 2.56	$ 2.27
Discontinued Operations		0	0	0	0.21
Earnings Per Share, Basic		1.52	1.42	2.56	2.48
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share		1.52	1.41	2.56	2.26
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share		0	0	0	0.21
Earnings Per Share, Diluted		1.52	1.41	2.56	2.47
Dividends per Common Share		$ 0.425	$ 0.41	$ 1.275	$ 1.23
Average Common Shares Outstanding - Basic		242.6	242.6	242.6	242.6
Weighted Average Number of Shares Outstanding, Diluted		242.9	243.9	243.0	243.8
Union Electric Company
Operating Revenues:
Electric		$ 1,144	$ 1,151	$ 2,682	$ 2,752
Gas		20	19	90	101
Other Revenue, Net		1	1	1	2
Total operating revenues		1,165	1,171	2,773	2,855
Operating Expenses:
Fuel		205	259	574	670
Purchased power		77	29	169	87
Gas purchased for resale		6	5	33	43
Other operations and maintenance		220	233	670	673
Provision for Callaway construction and operating license		0	0	0	69
Depreciation and amortization		130	125	384	367
Taxes other than income taxes		96	97	252	262
Total operating expenses		734	748	2,082	2,171
Operating Income		431	423	691	684
Other Income and Expenses:
Miscellaneous income		14	14	38	37
Miscellaneous expense		2	3	6	8
Total other income (expense)		12	11	32	29
Interest Charges		53	54	158	164
Income Before Income Taxes		390	380	565	549
Income Taxes		148	140	215	205
Net Income (Loss)		242	240	350	344
Other Comprehensive Income		0	0	0	0
Comprehensive Income		242	240	350	344
Net Income (Loss):
Net Income (Loss)		242	240	350	344
Earnings Per Share, Diluted [Abstract]
Preferred Stock Dividends		1	1	3	3
Net Income Available to Common Stockholder		241	239	347	341
Ameren Illinois Company
Operating Revenues:
Electric		562	540	1,365	1,316
Gas		114	115	530	597
Total operating revenues		676	655	1,895	1,913
Operating Expenses:
Purchased power		110	128	304	317
Gas purchased for resale		28	33	194	277
Other operations and maintenance		198	202	592	606
Depreciation and amortization		80	74	237	220
Taxes other than income taxes		30	29	98	101
Total operating expenses		446	466	1,425	1,521
Operating Income		230	189	470	392
Other Income and Expenses:
Miscellaneous income		4	4	15	15
Miscellaneous expense		3	3	11	10
Total other income (expense)		1	1	4	5
Interest Charges		35	33	105	99
Income Before Income Taxes		196	157	369	298
Income Taxes		77	59	144	114
Net Income (Loss)		119	98	225	184
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		(1)	0	(3)	(2)
Comprehensive Income		118	98	222	182
Net Income (Loss):
Net Income (Loss)		119	98	225	184
Earnings Per Share, Diluted [Abstract]
Preferred Stock Dividends		0	0	2	2
Net Income Available to Common Stockholder		$ 119	$ 98	$ 223	$ 182

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