Consolidated Statement of Income (Loss) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Operating Revenues:
Electric	$ 1,513		$ 1,614		$ 2,823		$ 3,084
Gas	147		167		495		601
Operating Revenues	1,660		1,781		3,318		3,685
Operating Expenses:
Fuel	346		371		673		750
Purchased power	133		237		296		464
Gas purchased for resale	49		79		264		367
Other operations and maintenance	458		473		885		936
Asset impairments			2		628		2
Depreciation and amortization	195		194		394		389
Taxes other than income taxes	116		109		237		234
Total operating expenses	1,297		1,465		3,377		3,142
Operating Income (Loss)	363		316		(59)		543
Other Income and Expenses:
Miscellaneous income	20	[1]	17	[1]	37	[1]	33	[1]
Miscellaneous expense	7	[1]	5	[1]	22	[1]	10	[1]
Total other income (expense)	13		12		15		23
Interest Charges	112		104		225		223
Income (Loss) Before Income Taxes	264		224		(269)		343
Income Taxes (Benefit)	54		85		(76)		130
Net Income (Loss)	210		139		(193)		213
Less: Net Income (Loss) Attributable to Noncontrolling Interest	(1)		1		(1)		4
Net Income (Loss)	211	[2]	138	[2]	(192)	[2]	209	[2]
Earnings (Loss) per Common Share - Basic and Diluted	$ 0.87		$ 0.57		$ (0.79)		$ 0.87
Dividends per Common Share	$ 0.400		$ 0.385		$ 0.800		$ 0.770
Weighted Average Number of Shares Outstanding, Basic	246.6		241.2		242.6		240.9
Union Electric Company [Member]
Operating Revenues:
Electric	822		791		1,458		1,493
Gas	21		28		76		97
Other	1		3		1		4
Operating Revenues	844		822		1,535		1,594
Operating Expenses:
Fuel	177		204		357		433
Purchased power			26		20		46
Gas purchased for resale	5		11		37		51
Other operations and maintenance	206		231		408		464
Depreciation and amortization	109		98		217		198
Taxes other than income taxes	78		76		149		149
Total operating expenses	575		646		1,188		1,341
Operating Income (Loss)	269		176		347		253
Other Income and Expenses:
Miscellaneous income	18		16		33		29
Miscellaneous expense	4		3		7		6
Total other income (expense)	14		13		26		23
Interest Charges	56		45		112		99
Income (Loss) Before Income Taxes	227		144		261		177
Income Taxes (Benefit)	83		53		95		64
Net Income (Loss)	144		91		166		113
Preferred Stock Dividends	1		1		2		2
Net Income Available to Common Stockholder	143		90		164		111
Ameren Illinois Company [Member]
Operating Revenues:
Electric	437		483		868		925
Gas	127		139		420		505
Other			1				1
Operating Revenues	564		623		1,288		1,431
Operating Expenses:
Purchased power	162		196		352		407
Gas purchased for resale	44		67		227		315
Other operations and maintenance	186		181		354		349
Depreciation and amortization	55		54		110		106
Taxes other than income taxes	31		26		70		67
Total operating expenses	478		524		1,113		1,244
Operating Income (Loss)	86		99		175		187
Other Income and Expenses:
Miscellaneous income	2		1		3		3
Miscellaneous expense	2		1		13		2
Total other income (expense)					(10)		1
Interest Charges	31		35		64		70
Income (Loss) Before Income Taxes	55		64		101		118
Income Taxes (Benefit)	22		26		40		46
Net Income (Loss)	33		38		61		72
Preferred Stock Dividends	1		1		2		2
Net Income Available to Common Stockholder	32		37		59		70
Ameren Energy Generating Company [Member]
Operating Revenues:
Operating Revenues	194		260		388		501
Operating Expenses:
Fuel	125		130		230		241
Purchased power			18				18
Other operations and maintenance	45		45		92		90
Depreciation and amortization	23		25		46		49
Taxes other than income taxes	5		5		11		12
Total operating expenses	198		223		379		410
Operating Income (Loss)	(4)		37		9		91
Other Income and Expenses:
Interest Charges	12		14		26		31
Income (Loss) Before Income Taxes	(16)		23		(17)		60
Income Taxes (Benefit)	(10)		10		(8)		25
Net Income (Loss)	(6)		13		(9)		35
Less: Net Income (Loss) Attributable to Noncontrolling Interest	(2)				(4)		1
Net Income (Loss)	$ (4)		$ 13		$ (5)		$ 34

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

[2] Represents net income (loss) available to common stockholders.