Consolidated Statement Of Cash Flows (USD $) In Millions	9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010
Cash Flows From Operating Activities:
Net income (loss)	$ 500	[1]	$ 97	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Goodwill, impairment and other charges	126		589
Gain on sales of properties	(12)		(5)
Net mark-to-market (gain) loss on derivatives	15		(27)
Depreciation and amortization	587		588
Amortization of nuclear fuel	51		36
Amortization of debt issuance costs and premium/discounts	17		19
Deferred income taxes and investment tax credits, net	380		409
Allowance for equity funds used during construction	(25)	[1]	(40)	[1]
Other	8		13
Changes in assets and liabilities:
Receivables	52		(154)
Materials and supplies	(34)		39
Accounts and wages payable	(191)		(170)
Taxes accrued	94		99
Assets, other	64		(107)
Liabilities, other	(4)		89
Pension and other postretirement benefits	(98)		(12)
Counterparty collateral, net	37		(24)
Taum Sauk insurance recoveries, net of costs	(1)		57
Net cash provided by operating activities	1,566		1,496
Cash Flows From Investing Activities:
Capital expenditures	(758)		(757)
Nuclear fuel expenditures	(45)		(24)
Purchases of securities - nuclear decommissioning trust fund	(163)		(207)
Sales of securities - nuclear decommissioning trust fund	147		195
Proceeds from sales of properties	50		20
Other	12		(3)
Net cash used in investing activities	(757)		(776)
Cash Flows From Financing Activities:
Dividends on common stock	(279)		(276)
Capital issuance costs			(15)
Dividends paid to noncontrolling interest holders	(5)		(7)
Short-term debt and credit facility repayments, net	(379)		(325)
Redemptions, repurchases, and maturities:
Long-term debt	(150)		(106)
Preferred stock			(52)
Issuances of common stock	49		60
Generator advances for construction refunded, net of receipts	(73)		(18)
Other	5		5
Net cash used in financing activities	(832)		(734)
Net change in cash and cash equivalents	(23)		(14)
Cash and cash equivalents at beginning of year	545		622
Cash and cash equivalents at end of period	522		608
Union Electric Company [Member]
Cash Flows From Operating Activities:
Net income (loss)	304		367
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from regulatory disallowance	89
Depreciation and amortization	300		283
Amortization of nuclear fuel	51		36
Amortization of debt issuance costs and premium/discounts	5		2
Deferred income taxes and investment tax credits, net	203		266
Allowance for equity funds used during construction	(22)		(38)
Other	1		9
Changes in assets and liabilities:
Receivables	(46)		(160)
Materials and supplies	2		10
Accounts and wages payable	(142)		(96)
Taxes accrued	51		118
Assets, other	56		(148)
Liabilities, other	1		77
Pension and other postretirement benefits	2		(5)
Taum Sauk insurance recoveries, net of costs	(1)		57
Net cash provided by operating activities	854		778
Cash Flows From Investing Activities:
Capital expenditures	(402)		(445)
Nuclear fuel expenditures	(45)		(24)
Purchases of securities - nuclear decommissioning trust fund	(163)		(207)
Sales of securities - nuclear decommissioning trust fund	147		195
Other	4
Net cash used in investing activities	(459)		(481)
Cash Flows From Financing Activities:
Dividends on common stock	(219)		(176)
Dividends on preferred stock	(3)		(4)
Capital issuance costs			(4)
Redemptions, repurchases, and maturities:
Long-term debt			(66)
Preferred stock			(33)
Generator advances for construction refunded, net of receipts	(19)		10
Net cash used in financing activities	(241)		(273)
Net change in cash and cash equivalents	154		24
Cash and cash equivalents at beginning of year	202		267
Cash and cash equivalents at end of period	356		291
Ameren Illinois Company [Member]
Cash Flows From Operating Activities:
Net income (loss)	170		215	[2]
Income from discontinued operations, net of tax			(40)	[2]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	161		158	[2]
Amortization of debt issuance costs and premium/discounts	6		9	[2]
Deferred income taxes and investment tax credits, net	202		143	[2]
Other	(7)		(5)	[2]
Changes in assets and liabilities:
Receivables	104		(16)	[2]
Materials and supplies	(41)		(31)	[2]
Accounts and wages payable	(58)		(41)	[2]
Taxes accrued	(14)		22	[2]
Assets, other	24		(76)	[2]
Liabilities, other	(11)		14	[2]
Pension and other postretirement benefits	(98)		(6)	[2]
Operating cash flows provided by discontinued operations			113	[2]
Net cash provided by operating activities	438		459	[2]
Cash Flows From Investing Activities:
Capital expenditures	(261)		(215)	[2]
Returns from (advances to) ATXI for construction	49		(7)	[2]
Proceeds from intercompany note receivable - Genco			45	[2]
Net investing activities used in discontinued operations			(6)	[2]
Net cash used in investing activities	(212)		(183)	[2]
Cash Flows From Financing Activities:
Dividends on common stock	(238)		(100)	[2]
Dividends on preferred stock	(2)		(4)	[2]
Capital issuance costs			(4)	[2]
Redemptions, repurchases, and maturities:
Long-term debt	(150)		(40)	[2]
Preferred stock			(19)	[2]
Generator advances for construction refunded, net of receipts	(53)		(28)	[2]
Net financing activities used in discontinued operations			(107)	[2]
Capital contribution from parent	6			[2]
Other	5		5	[2]
Net cash used in financing activities	(432)		(297)	[2]
Net change in cash and cash equivalents	(206)		(21)	[2]
Cash and cash equivalents at beginning of year	322		306	[2]
Cash and cash equivalents at end of period	116		285	[2]
Ameren Energy Generating Company [Member]
Cash Flows From Operating Activities:
Net income (loss)	31		(62)
Adjustments to reconcile net income to net cash provided by operating activities:
Goodwill, impairment and other charges	36		170
Loss on sales of emission allowances			3
Gain on sales of properties	(12)		(5)
Net mark-to-market (gain) loss on derivatives	5		(2)
Depreciation and amortization	75		87
Amortization of debt issuance costs and premium/discounts	2		2
Deferred income taxes and investment tax credits, net	58		5
Changes in assets and liabilities:
Receivables	9		55
Materials and supplies	6		43
Accounts and wages payable	(16)		(20)
Taxes accrued	(6)		10
Assets, other	3		8
Liabilities, other	(9)		(4)
Pension and other postretirement benefits	(3)		3
Net cash provided by operating activities	179		293
Cash Flows From Investing Activities:
Capital expenditures	(112)		(71)
Proceeds from sales of properties	49		18
Money pool advances, net	(38)		(132)
Net cash used in investing activities	(101)		(185)
Cash Flows From Financing Activities:
Capital issuance costs			(4)
Short-term debt and credit facility repayments, net	(100)
Note payable - affiliates			(103)
Redemptions, repurchases, and maturities:
Capital contribution from parent	24
Net cash used in financing activities	(76)		(107)
Net change in cash and cash equivalents	2		1
Cash and cash equivalents at beginning of year	6		6
Cash and cash equivalents at end of period	$ 8		$ 7

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

[2] Prior period reflects the Ameren Illinois Merger as discussed in Note 1 - Summary of Significant Accounting Policies.