Consolidated Statement of Cash Flows (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013 Union Electric Company	Sep. 30, 2012 Union Electric Company	Sep. 30, 2013 Ameren Illinois Company	Sep. 30, 2012 Ameren Illinois Company
Cash Flows From Operating Activities:
Net income	$ 257		$ 181		$ 365	$ 403	$ 141	$ 132
Loss from discontinued operations, net of taxes	212		331
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	500		466		313	303	178	159
Amortization of nuclear fuel	46		63		46	63
FAC prudence review charge					26
Amortization of debt issuance costs and premium/discounts	18		13		6	5	11	7
Deferred income taxes and investment tax credits, net	258		249		62	217	120	127
Allowance for equity funds used during construction	(26)	[1]	(26)	[1]	(22)	(23)
Stock-based compensation costs	19		23
Other	14		(6)		1	7	(7)	(8)
Changes in assets and liabilities:
Receivables	(88)		(21)		(148)	(62)	66	58
Materials and supplies	7		(57)		27	(53)	(20)	(6)
Accounts and wages payable	(102)		(157)		(124)	(168)	31	(4)
Taxes accrued	104		95		260	59	(2)	(3)
Assets, other	20		(24)		59	(29)	(33)	(2)
Liabilities, other	(24)		61		(78)	22	1	42
Pension and other postretirement benefits	(34)		16		(12)	17	(13)	(8)
Counterparty collateral, net	34		21				34	23
Premiums paid on long-term debt repurchases			(138)			(62)		(76)
Net cash provided by operating activities - continuing operations	1,215		1,090
Net cash provided by operating activities - discontinued operations	99		222
Net cash provided by operating activities	1,314		1,312		781	699	507	441
Cash Flows From Investing Activities:
Capital expenditures	(943)		(762)		(480)	(445)	(462)	(309)
Nuclear fuel expenditures	(34)		(56)		(34)	(56)
Money pool advances, net					24
Purchases of securities - nuclear decommissioning trust fund	(147)		(341)		(147)	(341)
Sales and maturities of securities - nuclear decommissioning trust fund	134		326		134	326
Other	(1)		(6)		(3)	(5)	6	5
Net cash used in investing activities - continuing operations	(991)		(839)
Net cash used in investing activities - discontinued operations	(42)		(123)
Net cash used in investing activities	(1,033)		(962)		(506)	(521)	(456)	(304)
Cash Flows From Financing Activities:
Dividends on common stock	(291)		(284)		(320)	(300)	(45)	(132)
Dividends paid to noncontrolling interest holders	(5)		(5)
Dividends on preferred stock					(3)	(3)	(2)	(2)
Money pool borrowings, net							(3)
Short-term debt, net			(143)
Redemptions, repurchases and maturities of long-term debt			(754)			(422)		(332)
Issuances of long-term debt			882			482		400
Capital issuance costs			(7)			(4)		(3)
Other			4					4
Net cash used in financing activities - continuing operations	(296)		(307)
Net cash used in financing activities - discontinued operations
Net cash used in financing activities	(296)		(307)		(323)	(247)	(50)	(65)
Net change in cash and cash equivalents	(15)		43		(48)	(69)	1	72
Cash and cash equivalents at beginning of period	209		255
Cash and cash equivalents at end of period	194		298
Less cash and cash equivalents at end of period, discontinued operations	25		25
Cash and cash equivalents at beginning of period	184				148	201		21
Cash and cash equivalents at end of period, continuing operations	169		273		100	132	1	93
Noncash financing activity - dividends on common stock			$ (7)

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