Consolidated Balance Sheet (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Current Assets:
Cash and cash equivalents	$ 255		$ 545
Accounts receivable - trade (less allowance for doubtful accounts)	473		517
Unbilled revenue	324		406
Miscellaneous accounts and notes receivable	69		210
Materials and supplies	712	[1]	707	[1]
Mark-to-market derivative assets	115		129
Current regulatory assets	215	[2]	267
Other current assets	132		109
Total current assets	2,295		2,890
Property and Plant, Net	18,127	[3],[4]	17,853	[3],[4]
Investments and Other Assets:
Nuclear decommissioning trust fund	357		337
Goodwill	411		411	[5]
Intangible assets	7		7
Regulatory assets	1,603	[2]	1,263
Other assets	845		750
Total investments and other assets	3,223		2,768
TOTAL ASSETS	23,645		23,511
Current Liabilities:
Current maturities of long-term debt	179		155
Short-term debt	148		269
Accounts and wages payable	693		651
Taxes accrued	65		63
Interest accrued	101		107
Customer deposits	98		100
Mark-to-market derivative liabilities	161		161
Current regulatory liabilities	133	[2]	99
Other current liabilities	207		283
Total current liabilities	1,785		1,888
Credit Facility Borrowings			460
Long-term Debt, Net	6,677		6,853
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes, net	3,315		2,882
Accumulated deferred investment tax credits	79		90
Regulatory liabilities	1,502	[2]	1,319
Asset retirement obligations	428		475
Pension and other postretirement benefits	1,344		1,045
Other deferred credits and liabilities	447		615
Total deferred credits and other liabilities	7,115		6,426
Commitments and Contingencies (Notes 2, 10, 14 and 15)
Stockholders' Equity:
Common stock	2		2
Other paid-in capital, principally premium on common stock	5,598		5,520
Retained earnings	2,369		2,225
Accumulated other comprehensive income (loss)	(50)		(17)
Total stockholders' equity	7,919		7,730
Noncontrolling Interests	149		154
Total equity	8,068		7,884
TOTAL LIABILITIES AND EQUITY	23,645		23,511
Union Electric Company [Member]
Current Assets:
Cash and cash equivalents	201		202
Accounts receivable - trade (less allowance for doubtful accounts)	212		217
Accounts receivable - affiliates	1		6
Unbilled revenue	139		159
Miscellaneous accounts and notes receivable	42		116
Materials and supplies	348		341
Current regulatory assets	109		179
Other current assets	82		55
Total current assets	1,134		1,275
Property and Plant, Net	9,958		9,775
Investments and Other Assets:
Nuclear decommissioning trust fund	357		337
Intangible assets	7		2
Regulatory assets	855		694
Other assets	446		421
Total investments and other assets	1,665		1,454
TOTAL ASSETS	12,757		12,504
Current Liabilities:
Current maturities of long-term debt	178		5
Accounts and wages payable	414		326
Accounts payable - affiliates	73		75
Taxes accrued	74		76
Interest accrued	62		63
Current regulatory liabilities	57		23
Current accumulated deferred income taxes, net			43
Other current liabilities	84		89
Total current liabilities	942		700
Long-term Debt, Net	3,772		3,949
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes, net	2,132		1,908
Accumulated deferred investment tax credits	70		78
Regulatory liabilities	836		766
Asset retirement obligations	328		363
Pension and other postretirement benefits	491		369
Other deferred credits and liabilities	149		218
Total deferred credits and other liabilities	4,006		3,702
Commitments and Contingencies (Notes 2, 10, 14 and 15)
Stockholders' Equity:
Common stock	511		511
Other paid-in capital, principally premium on common stock	1,555		1,555
Preferred stock not subject to mandatory redemption	80		80
Retained earnings	1,891		2,007
Total stockholders' equity	4,037		4,153
TOTAL LIABILITIES AND EQUITY	12,757		12,504
Ameren Illinois Company [Member]
Current Assets:
Cash and cash equivalents	21		322
Accounts receivable - trade (less allowance for doubtful accounts)	201		230
Accounts receivable - affiliates	15		73
Unbilled revenue	146		205
Miscellaneous accounts and notes receivable	6		44
Materials and supplies	199		198
Current regulatory assets	306		260
Current accumulated deferred income taxes, net	58		43
Other current assets	65		63
Total current assets	1,017		1,438
Property and Plant, Net	4,770		4,576
Investments and Other Assets:
Tax receivable - Genco	56		72
Goodwill	411		411
Regulatory assets	748		747
Other assets	211		162
Total investments and other assets	1,426		1,392
TOTAL ASSETS	7,213		7,406
Current Liabilities:
Current maturities of long-term debt	1		150
Accounts and wages payable	133		182
Accounts payable - affiliates	103		82
Taxes accrued	15		26
Customer deposits	76		83
Mark-to-market derivative liabilities	99		82
Mark-to-market derivative liabilities - affiliates	200		172
Environmental remediation	63		72
Current regulatory liabilities	76		76
Other current liabilities	92		90
Total current liabilities	858		1,015
Long-term Debt, Net	1,657		1,657
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes, net	895		724
Accumulated deferred investment tax credits	7		8
Regulatory liabilities	666		553
Pension and other postretirement benefits	495		413
Other deferred credits and liabilities	183		460
Total deferred credits and other liabilities	2,246		2,158
Commitments and Contingencies (Notes 2, 10, 14 and 15)
Stockholders' Equity:
Common stock
Other paid-in capital, principally premium on common stock	1,965		1,952
Preferred stock not subject to mandatory redemption	62		62
Retained earnings	408		542
Accumulated other comprehensive income (loss)	17		20
Total stockholders' equity	2,452		2,576
TOTAL LIABILITIES AND EQUITY	7,213		7,406
Ameren Energy Generating Company [Member]
Current Assets:
Cash and cash equivalents	8		6
Advances to money pool	74		25
Accounts receivable - affiliates	89		126
Miscellaneous accounts and notes receivable	13		15
Materials and supplies	122		130
Mark-to-market derivative assets	12		26
Other current assets	7		4
Total current assets	325		332
Property and Plant, Net	2,231		2,248
Investments and Other Assets:
Intangible assets			3
Other assets	16		24
Total investments and other assets	16		27
TOTAL ASSETS	2,572		2,607
Current Liabilities:
Accounts and wages payable	71		62
Accounts payable - affiliates	13		23
Current portion of tax payable - Ameren Illinois	8		8
Taxes accrued	20		20
Interest accrued	13		13
Mark-to-market derivative liabilities	3		9
Mark-to-market derivative liabilities - affiliates			5
Current accumulated deferred income taxes, net			13
Other current liabilities	14		12
Total current liabilities	142		165
Credit Facility Borrowings			100
Long-term Debt, Net	824		824
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes, net	304		249
Accumulated deferred investment tax credits	2		3
Tax payable - Ameren Illinois	56		72
Asset retirement obligations	66		74
Pension and other postretirement benefits	141		88
Other deferred credits and liabilities	12		23
Total deferred credits and other liabilities	581		509
Commitments and Contingencies (Notes 2, 10, 14 and 15)
Stockholders' Equity:
Common stock
Other paid-in capital, principally premium on common stock	653		649
Retained earnings	437		393
Accumulated other comprehensive income (loss)	(72)		(44)
Total stockholders' equity	1,018		998
Noncontrolling Interests	7		11
Total equity	1,025		1,009
TOTAL LIABILITIES AND EQUITY	$ 2,572		$ 2,607

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

[2] Includes intercompany eliminations.

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

[4] 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 $229 million and $228 million at December 31, 2011 and 2010, respectively. The total accumulated depreciation associated with the two CTs was $52 million and $46 million at December 31, 2011 and 2010, respectively.

[5] Includes amounts for Ameren registrants and nonregistrant subsidiaries.