Consolidated Statement of Comprehensive Income (Loss) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income from Continuing Operations	$ 307	$ 311	$ 469	$ 512
Other Comprehensive Income (Loss), Net of Taxes
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(5)	0	5	1
Other Comprehensive Income (Loss), Net of Taxes	(5)	0	5	1
Comprehensive Income from Continuing Operations	302	311	474	513
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests	2	2	5	5
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation	300	309	469	508
Income (Loss) from Discontinued Operations, Net of Taxes	(3)	63	(212)	(331)
Other Comprehensive Income (Loss) from Discontinued Operations, Net of Taxes	(5)	41	(16)	60
Comprehensive Income (Loss) from Discontinued Operations	(8)	104	(228)	(271)
Less: Comprehensive Income from Discontinued Operations Attributable to Noncontrolling Interest	0	7	0	3
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Corporation	(8)	97	(228)	(274)
Comprehensive Income (Loss)	$ 292	$ 406	$ 241	$ 234