Segment Information (Tables)

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Schedule Of Segment Reporting Information By Segment

The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three months ended March 31, 2019 and 2018. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount.

Ameren

Three Months	Ameren Missouri		Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission			Other		Intersegment Eliminations			Ameren
2019
External revenues	$	751	$	386	$	320	$	99		$	—	$	—		$	1,556
Intersegment revenues	7		1		—		15			—		(23		)	—
Net income attributable to Ameren common shareholders	39		36		57		44		(a)	15		—			191
Capital expenditures	240		124		51		121			10		(2		)	544
2018
External revenues	$	784	$	399	$	311	$	91		$	—	$	—		$	1,585
Intersegment revenues	8		1		—		13			—		(22		)	—
Net income attributable to Ameren common shareholders	38		33		42		37		(a)	1		—			151
Capital expenditures	249		122		60		145			7		(4		)	579

(a) Ameren Transmission earnings include an allocation of financing costs from Ameren (parent).

Ameren Illinois

Three Months	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations			Ameren Illinois
2019
External revenues	$	387	$	320	$	55	$	—		$	762
Intersegment revenues	—		—		15		(15		)	—
Net income available to common shareholder	36		57		27		—			120
Capital expenditures	124		51		92		—			267
2018
External revenues	$	400	$	311	$	49	$	—		$	760
Intersegment revenues	—		—		13		(13		)	—
Net income available to common shareholder	33		42		20		—			95
Capital expenditures	122		60		118		—			300

Disaggregation of Revenue

The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three months ended March 31, 2019 and 2018. Economic factors affect the nature, timing, amount, and uncertainty of revenues and cash flows in a similar manner across customer classes. Revenues from alternative revenue programs have a similar distribution among customer classes as revenues from contracts with customers. Other revenues not associated with contracts with customers are presented in the Other customer classification, along with electric transmission and off-system revenues.

Ameren

Three Months	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas			Ameren Transmission		Other		Intersegment Eliminations			Ameren
2019
Residential	$	312		$	217	$	—		$	—	$	—	$	—		$	529
Commercial	239			123		—			—		—		—			362
Industrial	55			34		—			—		—		—			89
Other	98			13		—			114		—		(23		)	202
Total electric revenues	$	704		$	387	$	—		$	114	$	—	$	(23	)	$	1,182
Residential	$	38		$	—	$	246		$	—	$	—	$	—		$	284
Commercial	16			—		65			—		—		—			81
Industrial	2			—		4			—		—		—			6
Other	(2		)	—		5			—		—		—			3
Total gas revenues	$	54		$	—	$	320		$	—	$	—	$	—		$	374
Total revenues(a)	$	758		$	387	$	320		$	114	$	—	$	(23	)	$	1,556
2018
Residential	$	332		$	219	$	—		$	—	$	—	$	—		$	551
Commercial	252			124		—			—		—		—			376
Industrial	61			35		—			—		—		—			96
Other	96			22		—			104		—		(22		)	200
Total electric revenues	$	741		$	400	$	—		$	104	$	—	$	(22	)	$	1,223
Residential	$	41		$	—	$	243		$	—	$	—	$	—		$	284
Commercial	16			—		67			—		—		—			83
Industrial	2			—		6			—		—		—			8
Other	(8		)	—		(5		)	—		—		—			(13		)
Total gas revenues	$	51		$	—	$	311		$	—	$	—	$	—		$	362
Total revenues(a)	$	792		$	400	$	311		$	104	$	—	$	(22	)	$	1,585

(a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three months ended March 31, 2019 and 2018:

Three Months	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas			Ameren Transmission			Ameren
2019
Revenues from alternative revenue programs	$	15		$	22	$	(3	)	$	(5	)	$	29
Other revenues not from contracts with customers	5			3		1			—			9
2018
Revenues from alternative revenue programs	$	(4	)	$	31	$	(3	)	$	(4	)	$	20
Other revenues not from contracts with customers	14			10		1			—			25

Ameren Illinois

Three Months	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas			Ameren Illinois Transmission		Intersegment Eliminations			Total Ameren Illinois
2019
Residential	$	217	$	246		$	—	$	—		$	463
Commercial	123		65			—		—			188
Industrial	34		4			—		—			38
Other	13		5			70		(15		)	73
Total revenues(a)	$	387	$	320		$	70	$	(15	)	$	762
2018
Residential	$	219	$	243		$	—	$	—		$	462
Commercial	124		67			—		—			191
Industrial	35		6			—		—			41
Other	22		(5		)	62		(13		)	66
Total revenues(a)	$	400	$	311		$	62	$	(13	)	$	760

(a) The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the Ameren Illinois segments for the three months ended March 31, 2019 and 2018:

Three Months	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas			Ameren Illinois Transmission			Ameren Illinois
2019
Revenues from alternative revenue programs	$	22	$	(3	)	$	(5	)	$	14
Other revenues not from contracts with customers	3		1			—			4
2018
Revenues from alternative revenue programs	$	31	$	(3	)	$	(4	)	$	24
Other revenues not from contracts with customers	10		1			—			11