Consolidated Statement of Income (Loss) - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating Revenues:
Electric		$ 1,274	$ 1,250	$ 2,376	$ 2,393
Gas		153	151	485	564
Total operating revenues		1,427	1,401	2,861	2,957
Operating Expenses:
Fuel		166	205	369	411
Purchased power		135	101	273	240
Gas purchased for resale		41	46	193	282
Other operations and maintenance		435	427	835	828
Provision for Callaway construction and operating license		0	69	0	69
Depreciation and amortization		210	200	417	393
Taxes other than income taxes		115	116	229	241
Total operating expenses		1,102	1,164	2,316	2,464
Operating Income		325	237	545	493
Other Income and Expenses:
Miscellaneous income	[1]	16	16	36	35
Miscellaneous expense	[1]	6	6	13	17
Total other income (expense)		10	10	23	18
Interest Charges		95	89	190	177
Income Before Income Taxes		240	158	378	334
Income Taxes		92	59	123	125
Income from Continuing Operations		148	99	255	209
Income from Discontinued Operations, Net of Taxes		0	52	0	52
Net Income (Loss)		148	151	255	261
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		4	4	2	4
Comprehensive Income		151	154	254	262
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
Net Income from Continuing Operations Attributable to Noncontrolling Interests		1	1	3	3
Net Income (Loss):
Continuing Operations		147	98	252	206
Discontinued Operations		0	52	0	52
Net Income (Loss)		$ 147	$ 150	$ 252	$ 258
Earnings Per Share, Basic [Abstract]
Continuing Operations		$ 0.61	$ 0.40	$ 1.04	$ 0.85
Discontinued Operations		0	0.21	0	0.21
Earnings Per Share, Basic		0.61	0.61	1.04	1.06
Dividends per Common Share		$ 0.425	$ 0.41	$ 0.85	$ 0.82
Average Common Shares Outstanding - Basic		242.6	242.6	242.6	242.6
Union Electric Company
Operating Revenues:
Electric		$ 844	$ 859	$ 1,538	$ 1,601
Gas		23	24	70	82
Other Revenue, Net		0	1	0	1
Total operating revenues		867	884	1,608	1,684
Operating Expenses:
Fuel		166	205	369	411
Purchased power		50	19	92	58
Gas purchased for resale		6	7	27	38
Other operations and maintenance		238	229	450	440
Provision for Callaway construction and operating license		0	69	0	69
Depreciation and amortization		127	124	254	242
Taxes other than income taxes		83	85	156	165
Total operating expenses		670	738	1,348	1,423
Operating Income		197	146	260	261
Other Income and Expenses:
Miscellaneous income		9	12	24	23
Miscellaneous expense		2	2	4	5
Total other income (expense)		7	10	20	18
Interest Charges		53	55	105	110
Income Before Income Taxes		151	101	175	169
Income Taxes		58	39	67	65
Net Income (Loss)		93	62	108	104
Other Comprehensive Income		0	0	0	0
Comprehensive Income		93	62	108	104
Net Income (Loss):
Net Income (Loss)		93	62	108	104
Earnings Per Share, Basic [Abstract]
Preferred Stock Dividends		1	1	2	2
Net Income Available to Common Stockholder		92	61	106	102
Ameren Illinois Company
Operating Revenues:
Electric		411	386	803	776
Gas		131	127	416	482
Total operating revenues		542	513	1,219	1,258
Operating Expenses:
Purchased power		90	87	194	189
Gas purchased for resale		35	39	166	244
Other operations and maintenance		200	202	394	404
Depreciation and amortization		80	73	157	146
Taxes other than income taxes		30	29	68	72
Total operating expenses		435	430	979	1,055
Operating Income		107	83	240	203
Other Income and Expenses:
Miscellaneous income		6	4	11	11
Miscellaneous expense		3	2	8	7
Total other income (expense)		3	2	3	4
Interest Charges		35	33	70	66
Income Before Income Taxes		75	52	173	141
Income Taxes		29	20	67	55
Net Income (Loss)		46	32	106	86
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		(1)	(1)	(2)	(2)
Comprehensive Income		45	31	104	84
Net Income (Loss):
Net Income (Loss)		46	32	106	86
Earnings Per Share, Basic [Abstract]
Preferred Stock Dividends		1	1	2	2
Net Income Available to Common Stockholder		$ 45	$ 31	$ 104	$ 84

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