Consolidated Statement of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Income from Continuing Operations	$ 148	$ 99	$ 255	$ 209
Other Comprehensive Income from Continuing Operations, Net of Taxes
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	4	4	2	4
Comprehensive Income from Continuing Operations	152	103	257	213
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests	1	1	3	3
Comprehensive Income from Continuing Operations Attributable to Ameren Common Shareholders	151	102	254	210
Income from Discontinued Operations, Net of Taxes	0	52	0	52
Other Comprehensive Income from Discontinued Operations, Net of Tax	0	0	0	0
Comprehensive Income from Discontinued Operations Attributable to Ameren Common Shareholders	0	52	0	52
Comprehensive Income Attributable to Ameren Common Shareholders	$ 151	$ 154	$ 254	$ 262