Consolidated Statement of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net Income from Continuing Operations	$ 56	$ 39
Other Comprehensive Income, Net of Taxes	0	0
Comprehensive Income from Continuing Operations	56	39
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests	2	2
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation	54	37
Net Loss from Discontinued Operations	(199)	(442)
Other Comprehensive Income (Loss) from Discontinued Operations, Net of Taxes	(7)	15
Comprehensive Loss from Discontinued Operations	(206)	(427)
Less: Comprehensive Loss from Discontinued Operations Attributable to Noncontrolling Interest	0	(2)
Comprehensive Loss from Discontinued Operations Attributable to Ameren Corporation	(206)	(425)
Comprehensive Income (Loss)	$ (152)	$ (388)