Segment Information (Tables)

12 Months Ended

Dec. 31, 2019

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, 2019, 2018, and 2017. 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
2019
External revenues	$	3,212	$	1,487	$	791	$	401		$	—		$	—			$	5,891
Intersegment revenues	31		17		6		63		(a)	—			(98		)		19		(b)
Depreciation and amortization	556		273		78		84			4			—				995
Interest income	26		6		—		1			5			(5		)		33
Interest charges	178		71		38		74		(c)	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		(a)	—			(93		)		—
Depreciation and amortization	550		259		65		77			4			—				955
Interest income	28		6		—		—			4			(5		)		33
Interest charges	200		73		38		75		(c)	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
2017
External revenues	$	3,488	$	1,564	$	742	$	382		$	(2	)	$	—			$	6,174
Intersegment revenues	49		4		1		44		(a)	—			(98		)		—
Depreciation and amortization	533		239		59		60			5			—				896
Interest income	27		7		—		—			11			(11		)		34
Interest charges	207		73		36		67		(c)	19			(11		)		391
Income taxes	254		83		36		90			113			—				576
Net income (loss) attributable to Ameren common shareholders	323		131		60		140			(131		)	—				523
Capital expenditures	773		476		245		644			1			(7		)		2,132

(a) Ameren Transmission earns revenue from transmission service provided to Ameren Illinois Electric Distribution. See discussion of transactions above.

(b) 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.

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

(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
2019
External revenues	$	1,504	$	797	$	226		$	—		$	2,527
Intersegment revenues	—		—		62		(a)	(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		(a)	(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
2017
External revenues	$	1,568	$	743	$	216		$	—		$	2,527
Intersegment revenues	—		—		42		(a)	(42		)	—
Depreciation and amortization	239		59		43			—			341
Interest income	7		—		—			—			7
Interest charges	73		36		35			—			144
Income taxes	83		36		47			—			166
Net income available to common shareholder	131		60		77			—			268
Capital expenditures	476		245		355			—			1,076

(a)

Ameren Illinois Transmission earns revenue from transmission service provided to Ameren Illinois Electric Distribution. See discussion of transactions above.

Disaggregation of Revenue

The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the years ended December 31, 2019, 2018, and 2017. 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		Other			Intersegment Eliminations			Ameren
2019
Residential	$	1,403		$	848		$	—		$	—	$	—		$	—		$	2,251
Commercial	1,157			497			—			—		—			—			1,654
Industrial	278			127			—			—		—			—			405
Other	271			32		(a)	—			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		(a)	—		—			(2		)	73
Total gas revenues	$	134		$	—		$	797		$	—	$	—		$	(2	)	$	929
Total revenues(b)	$	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(b)	$	3,589		$	1,547		$	815		$	433	$	—		$	(93	)	$	6,291
2017
Residential	$	1,417		$	870		$	—		$	—	$	—		$	—		$	2,287
Commercial	1,208			527			—			—		—			—			1,735
Industrial	305			113			—			—		—			—			418
Other	481			58			—			426		(2		)	(96		)	867
Total electric revenues	$	3,411		$	1,568		$	—		$	426	$	(2	)	$	(96	)	$	5,307
Residential	$	77		$	—		$	531		$	—	$	—		$	—		$	608
Commercial	31			—			146			—		—			—			177
Industrial	4			—			12			—		—			—			16
Other	14			—			54			—		—			(2		)	66
Total gas revenues	$	126		$	—		$	743		$	—	$	—		$	(2	)	$	867
Total revenues(b)	$	3,537		$	1,568		$	743		$	426	$	(2	)	$	(98	)	$	6,174

(a) 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.

(b)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, 2019, 2018, and 2017:

	Ameren Missouri			Ameren Illinois Electric Distribution			Ameren Illinois Natural Gas			Ameren Transmission			Ameren
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
2017
Revenues from alternative revenue programs	$	(28	)	$	(5	)	$	5		$	13		$	(15	)
Other revenues not from contracts with customers	15			6			2			—			23

(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
2019
Residential	$	848		$	570		$	—	$	—		$	1,418
Commercial	497			154			—		—			651
Industrial	127			13			—		—			140
Other	32		(a)	60		(a)	288		(62		)	318
Total revenues(b)	$	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(b)	$	1,547		$	815		$	267	$	(53	)	$	2,576
2017
Residential	$	870		$	531		$	—	$	—		$	1,401
Commercial	527			146			—		—			673
Industrial	113			12			—		—			125
Other	58			54			258		(42		)	328
Total revenues(b)	$	1,568		$	743		$	258	$	(42	)	$	2,527

(a) 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.

(b) 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, 2019, 2018, and 2017:

	Ameren Illinois Electric Distribution			Ameren Illinois Natural Gas			Ameren Illinois Transmission			Ameren Illinois
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
2017
Revenues from alternative revenue programs	$	(5	)	$	5		$	9		$	9
Other revenues not from contracts with customers	6			2			—			8