Consolidated Statement Of Income (Loss) - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Revenues:
Electric		$ 5,196	$ 5,180	$ 4,913
Gas		880	918	1,140
Total operating revenues		6,076	6,098	6,053
Operating Expenses:
Fuel		745	878	826
Purchased power		621	514	461
Gas purchased for resale		341	415	615
Other operations and maintenance		1,676	1,694	1,684
Provision for Callaway construction and operating license		0	69	0
Depreciation and amortization		845	796	745
Taxes other than income taxes		467	473	468
Total operating expenses		4,695	4,839	4,799
Operating Income		1,381	1,259	1,254
Other Income and Expenses:
Miscellaneous income	[1]	74	74	79
Miscellaneous expense	[1]	32	30	22
Total other income (expense)		42	44	57
Interest charges		382	355	341
Income Before Income Taxes		1,041	948	970
Income taxes		382	363	377
Income from Continuing Operations		659	585	593
Income (Loss) from Discontinued Operations, Net of Tax		0	51	(1)
Net Income (Loss)		659	636	592
Pension and other postretirement activity, net of income taxes (benefit)		(20)	6	(12)
Comprehensive Income (Loss)		633	636	574
Less: Net Income (Loss) Attributable to Noncontrolling Interests:
Continuing Operations		6	6	6
Net Income (Loss):
Net income attributable to Ameren Corporation - continuing operations		653	579	587
Discontinued Operations		0	51	(1)
Net income attributable to Ameren common shareholders		$ 653	$ 630	$ 586
Earnings (Loss) per Common Share – Basic:
Continuing Operations - Basic		$ 2.69	$ 2.39	$ 2.42
Discontinued Operations - Basic		0.00	0.21	0.00
Earnings (Loss) per Common Share – Basic		2.69	2.60	2.42
Earnings (Loss) per Common Share – Diluted:
Continuing Operations - Diluted		2.68	2.38	2.40
Discontinued Operations - Diluted		0.00	0.21	0.00
Earnings (Loss) per Common Share – Diluted		2.68	2.59	2.40
Dividends per Common Share		$ 1.715	$ 1.655	$ 1.61
Average Common Shares Outstanding - Basic		242.6	242.6	242.6
Average Common Shares Outstanding - Diluted		243.4	243.6	244.4
Union Electric Company
Operating Revenues:
Electric		$ 3,394	$ 3,470	$ 3,388
Gas		128	137	164
Other		1	2	1
Total operating revenues		3,523	3,609	3,553
Operating Expenses:
Fuel		745	878	826
Purchased power		252	111	126
Gas purchased for resale		49	57	82
Other operations and maintenance		893	925	939
Provision for Callaway construction and operating license		0	69	0
Depreciation and amortization		514	492	473
Taxes other than income taxes		325	335	322
Total operating expenses		2,778	2,867	2,768
Operating Income		745	742	785
Other Income and Expenses:
Miscellaneous income		52	52	60
Miscellaneous expense		10	11	12
Total other income (expense)		42	41	48
Interest charges		211	219	211
Income Before Income Taxes		576	564	622
Income taxes		216	209	229
Net Income (Loss)		360	355	393
Other Comprehensive Income		0	0	0
Comprehensive Income (Loss)		360	355	393
Net Income (Loss):
Preferred Stock Dividends		3	3	3
Net Income Available to Common Stockholder		357	352	390
Ameren Illinois Company
Operating Revenues:
Electric		1,736	1,683	1,522
Gas		754	783	976
Total operating revenues		2,490	2,466	2,498
Operating Expenses:
Purchased power		399	420	343
Gas purchased for resale		292	358	533
Other operations and maintenance		804	797	771
Depreciation and amortization		319	295	263
Taxes other than income taxes		132	130	138
Total operating expenses		1,946	2,000	2,048
Operating Income		544	466	450
Other Income and Expenses:
Miscellaneous income		21	21	17
Miscellaneous expense		12	12	8
Total other income (expense)		9	9	9
Interest charges		140	131	112
Income Before Income Taxes		413	344	347
Income taxes		158	127	143
Net Income (Loss)		255	217	204
Pension and other postretirement activity, net of income taxes (benefit)		(5)	(3)	(3)
Comprehensive Income (Loss)		250	214	201
Net Income (Loss):
Preferred Stock Dividends		3	3	3
Net Income Available to Common Stockholder		$ 252	$ 214	$ 201

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