Consolidated Balance Sheet (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Current Assets:
Cash and cash equivalents	$ 209		$ 255
Accounts receivable - trade (less allowance for doubtful accounts)	401		473
Unbilled revenue	322		324
Miscellaneous accounts and notes receivable	95		69
Materials and supplies	704	[1]	712	[1]
Mark-to-market derivative assets	125		115
Current regulatory assets	247		215
Current accumulated deferred income taxes, net	171		20
Other current assets	95		112
Total current assets	2,369		2,295
Property, Plant and Equipment, Net	16,096	[2],[3]	18,127	[2],[3]
Investments and Other Assets:
Nuclear decommissioning trust fund	408		357
Goodwill	411		411
Intangible assets	16		7
Regulatory assets	1,786		1,603
Other assets	749		845
Total investments and other assets	3,370		3,223
TOTAL ASSETS	21,835		23,645
Current Liabilities:
Current maturities of long-term debt	355		179
Short-term debt			148
Accounts and wages payable	625		693
Taxes accrued	68		65
Interest accrued	99		101
Customer deposits	108		98
Mark-to-market derivative liabilities	155		161
Current regulatory liabilities	100		133
Other current liabilities	188		207
Total current liabilities	1,698		1,785
Long-term Debt, Net	6,626		6,677
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes, net	2,792		3,315
Accumulated deferred investment tax credits	72		79
Regulatory liabilities	1,589		1,502
Asset retirement obligations	445		428
Pension and other postretirement benefits	1,178		1,344
Other deferred credits and liabilities	668		447
Total deferred credits and other liabilities	6,744		7,115
Commitments and Contingencies (Notes 2, 10, 14 and 15)
Stockholders' Equity:
Common stock	2		2
Other paid-in capital, principally premium on common stock	5,616		5,598
Preferred stock not subject to mandatory redemption	142	[4]	142	[4]
Retained earnings	1,006		2,369
Accumulated other comprehensive income (loss)	(8)		(50)
Total stockholders' equity	6,616		7,919
Noncontrolling Interests	151		149
Total equity	6,767		8,068
TOTAL LIABILITIES AND EQUITY	21,835		23,645
Union Electric Company [Member]
Current Assets:
Cash and cash equivalents	148		201
Advances to money pool	24
Accounts receivable - trade (less allowance for doubtful accounts)	161		212
Accounts receivable - affiliates	4		1
Unbilled revenue	145		139
Miscellaneous accounts and notes receivable	48		42
Materials and supplies	397		348
Current regulatory assets	163		109
Current accumulated deferred income taxes, net	26		8
Other current assets	69		82
Total current assets	1,159		1,134
Property, Plant and Equipment, Net	10,161	[3]	9,958	[3]
Investments and Other Assets:
Nuclear decommissioning trust fund	408		357
Intangible assets	14		7
Regulatory assets	852		855
Other assets	449		446
Total investments and other assets	1,723		1,665
TOTAL ASSETS	13,043		12,757
Current Liabilities:
Current maturities of long-term debt	205		178
Accounts and wages payable	345		414
Accounts payable - affiliates	66		73
Taxes accrued	28		74
Interest accrued	60		62
Current regulatory liabilities	18		57
Other current liabilities	77		84
Total current liabilities	799		942
Long-term Debt, Net	3,801		3,772
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes, net	2,443		2,132
Accumulated deferred investment tax credits	64		70
Regulatory liabilities	917		836
Asset retirement obligations	346		328
Pension and other postretirement benefits	461		491
Other deferred credits and liabilities	158		149
Total deferred credits and other liabilities	4,389		4,006
Commitments and Contingencies (Notes 2, 10, 14 and 15)
Stockholders' Equity:
Common stock	511		511
Other paid-in capital, principally premium on common stock	1,556		1,555
Preferred stock not subject to mandatory redemption	80		80
Retained earnings	1,907		1,891
Total stockholders' equity	4,054		4,037
TOTAL LIABILITIES AND EQUITY	13,043		12,757
Ameren Illinois Company [Member]
Current Assets:
Cash and cash equivalents	0		21
Accounts receivable - trade (less allowance for doubtful accounts)	182		201
Accounts receivable - affiliates	10		15
Unbilled revenue	146		146
Miscellaneous accounts and notes receivable	22		6
Materials and supplies	173		199
Current regulatory assets	84		306
Current accumulated deferred income taxes, net	85		58
Other current assets	47		65
Total current assets	749		1,017
Property, Plant and Equipment, Net	5,052		4,770
Investments and Other Assets:
Intercompany tax receivable – Genco	39		56
Goodwill	411		411
Regulatory assets	934		748
Other assets	97		211
Total investments and other assets	1,481		1,426
TOTAL ASSETS	7,282		7,213
Current Liabilities:
Current maturities of long-term debt	150		1
Borrowings from money pool	24
Accounts and wages payable	146		133
Accounts payable - affiliates	86		103
Taxes accrued	18		15
Customer deposits	85		76
Mark-to-market derivative liabilities	77		99
Mark-to-market derivative liabilities - affiliates			200
Environmental remediation	37		63
Current regulatory liabilities	82		76
Other current liabilities	92		92
Total current liabilities	797		858
Long-term Debt, Net	1,577		1,657
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes, net	1,025		895
Accumulated deferred investment tax credits	5		7
Regulatory liabilities	672		666
Pension and other postretirement benefits	406		495
Other deferred credits and liabilities	399		183
Total deferred credits and other liabilities	2,507		2,246
Commitments and Contingencies (Notes 2, 10, 14 and 15)
Stockholders' Equity:
Other paid-in capital, principally premium on common stock	1,965		1,965
Preferred stock not subject to mandatory redemption	62		62
Retained earnings	360		408
Accumulated other comprehensive income (loss)	14		17
Total stockholders' equity	2,401		2,452
TOTAL LIABILITIES AND EQUITY	$ 7,282		$ 7,213

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

[2] Includes amounts for Ameren registrant and nonregistrant subsidiaries as well as intercompany eliminations.

[3] Amounts in Ameren and Ameren Missouri include two electric generation CTs under two separate capital lease agreements. The gross asset value of those agreements was $228 million and $229 million at December 31, 2012, and 2011, respectively. The total accumulated depreciation associated with the two CTs was $52 million and $52 million at December 31, 2012, and 2011, respectively. In addition, Ameren Missouri has investments in debt securities, which are classified as held-to-maturity, related to the two CTs from the city of Bowling Green and Audrain County. As of December 31, 2012, and 2011, the carrying value of these debt securities was $304 million and $309 million, respectively.

[4] (b)Preferred stock not subject to mandatory redemption of Ameren's subsidiaries was included in "Noncontrolling Interests" on Ameren's consolidated balance sheet.