Consolidated Statement of Income (Loss) - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Operating Revenues:
Electric		$ 1,102	$ 1,143
Gas		332	413
Total operating revenues		1,434	1,556
Operating Expenses:
Fuel		203	206
Purchased power		138	139
Gas purchased for resale		152	236
Other operations and maintenance		400	401
Depreciation and amortization		207	193
Taxes other than income taxes		114	125
Total operating expenses		1,214	1,300
Operating Income		220	256
Other Income and Expenses:
Miscellaneous income	[1]	20	19
Miscellaneous expense	[1]	7	11
Total other income (expense)		13	8
Interest Charges		95	88
Income Before Income Taxes		138	176
Income Taxes		31	66
Income from Continuing Operations		107	110
Income (Loss) from Discontinued Operations, Net of Taxes		0	0
Net Income (Loss)		107	110
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		(2)	0
Comprehensive Income		103	108
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
Net Income from Continuing Operations Attributable to Noncontrolling Interests		2	2
Net Income (Loss):
Continuing Operations		105	108
Discontinued Operations		0	0
Net Income (Loss)		$ 105	$ 108
Earnings Per Share, Basic [Abstract]
Continuing Operations		$ 0.43	$ 0.45
Discontinued Operations		0	0
Earnings Per Share, Basic		0.43	0.45
Dividends per Common Share		$ 0.425	$ 0.41
Average Common Shares Outstanding - Basic		242.6	242.6
Union Electric Company
Operating Revenues:
Electric		$ 694	$ 742
Gas		47	58
Total operating revenues		741	800
Operating Expenses:
Fuel		203	206
Purchased power		42	39
Gas purchased for resale		21	31
Other operations and maintenance		212	211
Depreciation and amortization		127	118
Taxes other than income taxes		73	80
Total operating expenses		678	685
Operating Income		63	115
Other Income and Expenses:
Miscellaneous income		15	11
Miscellaneous expense		2	3
Total other income (expense)		13	8
Interest Charges		52	55
Income Before Income Taxes		24	68
Income Taxes		9	26
Net Income (Loss)		15	42
Other Comprehensive Income		0	0
Comprehensive Income		15	42
Net Income (Loss):
Net Income (Loss)		15	42
Earnings Per Share, Basic [Abstract]
Preferred Stock Dividends		1	1
Net Income Available to Common Stockholder		14	41
Ameren Illinois Company
Operating Revenues:
Electric		392	390
Gas		285	355
Total operating revenues		677	745
Operating Expenses:
Purchased power		104	102
Gas purchased for resale		131	205
Other operations and maintenance		194	202
Depreciation and amortization		77	73
Taxes other than income taxes		38	43
Total operating expenses		544	625
Operating Income		133	120
Other Income and Expenses:
Miscellaneous income		5	7
Miscellaneous expense		5	5
Total other income (expense)			2
Interest Charges		35	33
Income Before Income Taxes		98	89
Income Taxes		38	35
Net Income (Loss)		60	54
Pension and other postretirement benefit plan activity, net of income taxes (benefit)		(1)	(1)
Comprehensive Income		59	53
Net Income (Loss):
Net Income (Loss)		60	54
Earnings Per Share, Basic [Abstract]
Preferred Stock Dividends		1	1
Net Income Available to Common Stockholder		$ 59	$ 53

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