Consolidated Statement of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Income from Continuing Operations	$ 99	$ 151	$ 209	$ 250
Other Comprehensive Income from Continuing Operations, Net Of Taxes
Other Comprehensive Income from Continuing Operations, Net of Taxes
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	4	3	$ 4	$ 3
Comprehensive Income from Continuing Operations	103	154	213	253
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests	1	1	3	3
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation	102	153	210	250
Income (Loss) from Discontinued Operations, Net of Taxes	52	(1)	52	(2)
Other Comprehensive Loss from Discontinued Operations, Net of Taxes	0	0	0	0
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Corporation	52	(1)	52	(2)
Comprehensive Income	$ 154	$ 152	$ 262	$ 248