Segment Information (Tables)

12 Months Ended

Dec. 31, 2020

Segment Reporting [Abstract]

Schedule Of Segment Reporting Information, By Segment

The following tables present information about the reported revenue and specified items reflected in net income attributable to common shareholders and capital expenditures by segment at Ameren and Ameren Illinois for the years ended December 31, 2020, 2019, and 2018. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount.

Ameren

	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission			Other		Intersegment Eliminations			Ameren
2020
External revenues	$	3,069		$	1,496	$	760	$	469		$	—	$	—		$	5,794
Intersegment revenues	40			2		—		54			—		(96)			—
Depreciation and amortization	604			288		81		98			4		—			1,075
Interest income	26			2		—		1			4		(4)			29
Interest charges	190			72		41		78		(a)	42		(4)			419
Income taxes (benefit)	34			42		36		78			(35)		—			155
Net income (loss) attributable to Ameren common shareholders	436			143		99		216			(23)		—			871
Capital expenditures	1,666		(b)	543		301		716			5		2			3,233		(b)
2019
External revenues	$	3,212		$	1,487	$	791	$	401		$	—	$	—		$	5,891
Intersegment revenues	31			17		6		63			—		(98)			19		(c)
Depreciation and amortization	556			273		78		84			4		—			995
Interest income	26			6		—		1			5		(5)			33
Interest charges	178			71		38		74		(a)	25		(5)			381
Income taxes (benefit)	68			45		30		64			(25)		—			182
Net income (loss) attributable to Ameren common shareholders	426			146		84		185			(13)		—			828
Capital expenditures	1,076			518		318		528			3		(32)		(d)	2,411
2018
External revenues	$	3,555		$	1,544	$	814	$	378		$	—	$	—		$	6,291
Intersegment revenues	34			3		1		55			—		(93)			—
Depreciation and amortization	550			259		65		77			4		—			955
Interest income	28			6		—		—			4		(5)			33
Interest charges	200			73		38		75		(a)	19		(4)			401
Income taxes (benefit)	124			41		25		56			(9)		—			237
Net income (loss) attributable to Ameren common shareholders	478			136		70		164			(33)		—			815
Capital expenditures	914			503		311		562			5		(9)			2,286

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

(b)Includes $564 million at Ameren and Ameren Missouri for the acquisition of the High Prairie Renewable Energy Center for the year ended December 31, 2020.

(c)Intersegment revenues at Ameren include $14 million and $5 million of revenue from Ameren Illinois Electric Distribution and Ameren Illinois Natural Gas, respectively, for the year ended December 31, 2019, for a software licensing agreement with Ameren Missouri. Under authoritative accounting guidance for rate-regulated entities, the revenue recognized by Ameren Illinois was not eliminated upon consolidation. See Note 13 – Related-party Transactions for additional information.

(d)Intersegment capital expenditure eliminations include $24 million of eliminations for the year ended December 31, 2019, for a software licensing agreement between Ameren Illinois and Ameren Missouri. See Note 13 – Related-party Transactions for additional information.

Ameren Illinois

	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
2020
External revenues	$	1,498	$	760	$	277	$	—	$	2,535
Intersegment revenues	—		—		52		(52)		—
Depreciation and amortization	288		81		65		—		434
Interest income	2		—		1		—		3
Interest charges	72		41		42		—		155
Income taxes	42		36		46		—		124
Net income available to common shareholder	143		99		137		—		379
Capital expenditures	543		301		603		—		1,447
2019
External revenues	$	1,504	$	797	$	226	$	—	$	2,527
Intersegment revenues	—		—		62		(62)		—
Depreciation and amortization	273		78		55		—		406
Interest income	6		—		—		—		6
Interest charges	71		38		38		—		147
Income taxes	45		30		35		—		110
Net income available to common shareholder	146		84		113		—		343
Capital expenditures	518		318		372		—		1,208
2018
External revenues	$	1,547	$	815	$	214	$	—	$	2,576
Intersegment revenues	—		—		53		(53)		—
Depreciation and amortization	259		65		50		—		374
Interest income	6		—		—		—		6
Interest charges	73		38		38		—		149
Income taxes	41		25		32		—		98
Net income available to common shareholder	136		70		98		—		304
Capital expenditures	503		311		444		—		1,258

Disaggregation of Revenue

The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the years ended December 31, 2020, 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

	Ameren Missouri			Ameren Illinois Electric Distribution			Ameren Illinois Natural Gas			Ameren Transmission		Intersegment Eliminations		Ameren
2020
Residential	$	1,373		$	867		$	—		$	—	$	—	$	2,240
Commercial	1,025			486			—			—		—		1,511
Industrial	261			124			—			—		—		385
Other	325			21			—			523		(94)		775
Total electric revenues	$	2,984		$	1,498		$	—		$	523	$	(94)	$	4,911
Residential	$	76		$	—		$	541		$	—	$	—	$	617
Commercial	29			—			136			—		—		165
Industrial	4			—			14			—		—		18
Other	16			—			69			—		(2)		83
Total gas revenues	$	125		$	—		$	760		$	—	$	(2)	$	883
Total revenues(a)	$	3,109		$	1,498		$	760		$	523	$	(96)	$	5,794
2019
Residential	$	1,403		$	848		$	—		$	—	$	—	$	2,251
Commercial	1,157			497			—			—		—		1,654
Industrial	278			127			—			—		—		405
Other	271			32		(b)	—			464		(96)		671
Total electric revenues	$	3,109		$	1,504		$	—		$	464	$	(96)	$	4,981
Residential	$	81		$	—		$	570		$	—	$	—	$	651
Commercial	34			—			154			—		—		188
Industrial	4			—			13			—		—		17
Other	15			—			60		(b)	—		(2)		73
Total gas revenues	$	134		$	—		$	797		$	—	$	(2)	$	929
Total revenues(a)	$	3,243		$	1,504		$	797		$	464	$	(98)	$	5,910
2018
Residential	$	1,560		$	867		$	—		$	—	$	—	$	2,427
Commercial	1,271			511			—			—		—		1,782
Industrial	312			130			—			—		—		442
Other	308		(c)	39			—			433		(92)		688		(c)
Total electric revenues	$	3,451		$	1,547		$	—		$	433	$	(92)	$	5,339
Residential	$	90		$	—		$	581		$	—	$	—	$	671
Commercial	37			—			159			—		—		196
Industrial	4			—			17			—		—		21
Other	7			—			58			—		(1)		64
Total gas revenues	$	138		$	—		$	815		$	—	$	(1)	$	952
Total revenues(a)	$	3,589		$	1,547		$	815		$	433	$	(93)	$	6,291

(a)The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the years ended December 31, 2020, 2019, and 2018:

	Ameren Missouri		Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Ameren
2020
Revenues from alternative revenue programs	$	(14)	$	(20)	$	20	$	50	$	36
Other revenues not from contracts with customers	25		8		2		1		36
2019
Revenues from alternative revenue programs	$	35	$	(74)	$	—	$	(31)	$	(70)
Other revenues not from contracts with customers	19		7		2		—		28
2018
Revenues from alternative revenue programs	$	(8)	$	(3)	$	(23)	$	(25)	$	(59)
Other revenues not from contracts with customers	24		16		2		—		42

(b)Includes $14 million and $5 million for Ameren Illinois Electric Distribution and Ameren Illinois Natural Gas, respectively, for the year ended December 31, 2019, for a software licensing agreement with Ameren Missouri. See Note 13 – Related-party Transactions for additional information.

(c)Includes $60 million for the year ended December 31, 2018, for the reduction to revenue for the excess amounts collected in rates to be refunded related to the TCJA from January 1, 2018, through July 31, 2018. See Note 2 – Rate and Regulatory Matters for additional information.

Ameren Illinois

	Ameren Illinois Electric Distribution			Ameren Illinois Natural Gas			Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
2020
Residential	$	867		$	541		$	—	$	—	$	1,408
Commercial	486			136			—		—		622
Industrial	124			14			—		—		138
Other	21			69			329		(52)		367
Total revenues(a)	$	1,498		$	760		$	329	$	(52)	$	2,535
2019
Residential	$	848		$	570		$	—	$	—	$	1,418
Commercial	497			154			—		—		651
Industrial	127			13			—		—		140
Other	32		(b)	60		(b)	288		(62)		318
Total revenues(a)	$	1,504		$	797		$	288	$	(62)	$	2,527
2018
Residential	$	867		$	581		$	—	$	—	$	1,448
Commercial	511			159			—		—		670
Industrial	130			17			—		—		147
Other	39			58			267		(53)		311
Total revenues(a)	$	1,547		$	815		$	267	$	(53)	$	2,576

(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 years ended December 31, 2020, 2019, and 2018:

	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Ameren Illinois
2020
Revenues from alternative revenue programs	$	(20)	$	20	$	42	$	42
Other revenues not from contracts with customers	8		2		—		10
2019
Revenues from alternative revenue programs	$	(74)	$	—	$	(33)	$	(107)
Other revenues not from contracts with customers	7		2		—		9
2018
Revenues from alternative revenue programs	$	(3)	$	(23)	$	(25)	$	(51)
Other revenues not from contracts with customers	16		2		—		18

(b)Includes $14 million and $5 million for Ameren Illinois Electric Distribution and Ameren Illinois Natural Gas, respectively, for the year ended December 31, 2019, for a software licensing agreement with Ameren Missouri. See Note 13 – Related-party Transactions for additional information.