Consolidated Statement Of Income (Loss) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Operating Revenues:
Electric	$ 4,832,000,000		$ 4,857,000,000		$ 5,147,000,000
Gas	1,006,000,000		924,000,000		1,001,000,000
Total operating revenues	5,838,000,000		5,781,000,000		6,148,000,000
Operating Expenses:
Fuel	845,000,000		714,000,000		866,000,000
Purchased power	502,000,000		780,000,000		952,000,000
Gas purchased for resale	526,000,000		472,000,000		570,000,000
Other operations and maintenance	1,617,000,000		1,511,000,000		1,562,000,000
Loss from regulatory disallowance					89,000,000
Impairment and other charges
Depreciation and amortization	706,000,000		673,000,000		643,000,000
Taxes other than income taxes	458,000,000		443,000,000		433,000,000
Total operating expenses	4,654,000,000		4,593,000,000		5,115,000,000
Operating Income	1,184,000,000		1,188,000,000		1,033,000,000
Other Income and Expenses:
Miscellaneous income	69,000,000	[1]	70,000,000	[1]	68,000,000	[1]
Miscellaneous expense	26,000,000	[1]	37,000,000	[1]	23,000,000	[1]
Total other income (expense)	43,000,000		33,000,000		45,000,000
Interest charges	398,000,000		392,000,000		387,000,000
Income Before Income Taxes	829,000,000		829,000,000		691,000,000
Income taxes	311,000,000	[1]	307,000,000	[1]	254,000,000	[1]
Income from Continuing Operations	518,000,000		522,000,000		437,000,000
Income (Loss) from Discontinued Operations, Net of Tax (Note 16)	(223,000,000)		(1,496,000,000)		89,000,000
Net Income (Loss)	295,000,000		(974,000,000)		526,000,000
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
Continuing Operations	6,000,000		6,000,000		6,000,000
Discontinued Operations			(6,000,000)		1,000,000
Net Income (Loss):
Net income attributable to Ameren Corporation - continuing operations	512,000,000		516,000,000		431,000,000
Discontinued Operations	(223,000,000)		(1,490,000,000)		88,000,000
Net income (loss) attributable to Ameren Corporation	289,000,000		(974,000,000)		519,000,000
Pension and other postretirement activity, net of income taxes (benefit)	30,000,000		(8,000,000)		(19,000,000)
Comprehensive Income (Loss)	300,000,000		(932,000,000)		486,000,000
Earnings (Loss) per Common Share – Basic:
Continuing Operations - Basic	$ 2.11		$ 2.13		$ 1.79
Discontinued Operations - Basic	$ (0.92)		$ (6.14)		$ 0.36
Earnings (Loss) per Common Share – Basic	$ 1.19		$ (4.01)		$ 2.15
Earnings (Loss) per Common Share – Diluted:
Continuing Operations - Diluted	$ 2.10		$ 2.13		$ 1.79
Discontinued Operations - Diluted	$ (0.92)		$ (6.14)		$ 0.36
Earnings (Loss) per Common Share – Diluted	$ 1.18		$ (4.01)		$ 2.15
Dividends per Common Share	$ 1.60		$ 1.600		$ 1.555
Average Common Shares Outstanding - Basic	242.6		242.6		241.5
Average Common Shares Outstanding - Diluted	244.5		243.0		242.1
Union Electric Company
Operating Revenues:
Electric	3,379,000,000		3,132,000,000		3,222,000,000
Gas	161,000,000		139,000,000		156,000,000
Other	1,000,000		1,000,000		5,000,000
Total operating revenues	3,541,000,000		3,272,000,000		3,383,000,000
Operating Expenses:
Fuel	845,000,000		714,000,000		866,000,000
Purchased power	127,000,000		78,000,000		104,000,000
Gas purchased for resale	78,000,000		64,000,000		77,000,000
Other operations and maintenance	915,000,000		827,000,000		934,000,000
Loss from regulatory disallowance					89,000,000
Depreciation and amortization	454,000,000		440,000,000		408,000,000
Taxes other than income taxes	319,000,000		304,000,000		296,000,000
Total operating expenses	2,738,000,000		2,427,000,000		2,774,000,000
Operating Income	803,000,000		845,000,000		609,000,000
Other Income and Expenses:
Miscellaneous income	58,000,000		63,000,000		61,000,000
Miscellaneous expense	11,000,000		14,000,000		10,000,000
Total other income (expense)	47,000,000		49,000,000		51,000,000
Interest charges	210,000,000		223,000,000		209,000,000
Income Before Income Taxes	640,000,000		671,000,000		451,000,000
Income taxes	242,000,000		252,000,000		161,000,000
Net Income (Loss)	398,000,000		419,000,000		290,000,000
Net Income (Loss):
Net income (loss) attributable to Ameren Corporation	398,000,000		419,000,000		290,000,000
Other Comprehensive Income
Comprehensive Income (Loss)	398,000,000		419,000,000		290,000,000
Preferred Stock Dividends	3,000,000		3,000,000		3,000,000
Net Income Available to Common Stockholder	395,000,000		416,000,000		287,000,000
Ameren Illinois Company
Operating Revenues:
Electric	1,461,000,000		1,739,000,000		1,940,000,000
Gas	847,000,000		786,000,000		846,000,000
Other	3,000,000				1,000,000
Total operating revenues	2,311,000,000		2,525,000,000		2,787,000,000
Operating Expenses:
Purchased power	380,000,000		705,000,000		853,000,000
Gas purchased for resale	448,000,000		408,000,000		492,000,000
Other operations and maintenance	693,000,000		684,000,000		640,000,000
Depreciation and amortization	243,000,000		221,000,000		215,000,000
Taxes other than income taxes	132,000,000		130,000,000		129,000,000
Total operating expenses	1,896,000,000		2,148,000,000		2,329,000,000
Operating Income	415,000,000		377,000,000		458,000,000
Other Income and Expenses:
Miscellaneous income	10,000,000		7,000,000		7,000,000
Miscellaneous expense	9,000,000		17,000,000		6,000,000
Total other income (expense)	1,000,000		(10,000,000)		1,000,000
Interest charges	143,000,000		129,000,000		136,000,000
Income Before Income Taxes	273,000,000		238,000,000		323,000,000
Income taxes	110,000,000		94,000,000		127,000,000
Net Income (Loss)	163,000,000		144,000,000		196,000,000
Net Income (Loss):
Net income (loss) attributable to Ameren Corporation	163,000,000		144,000,000		196,000,000
Pension and other postretirement activity, net of income taxes (benefit)	(3,000,000)		(3,000,000)		(3,000,000)
Comprehensive Income (Loss)	160,000,000		141,000,000		193,000,000
Preferred Stock Dividends	3,000,000		3,000,000		3,000,000
Net Income Available to Common Stockholder	$ 160,000,000		$ 141,000,000		$ 193,000,000

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