Selected Quarterly Information

12 Months Ended

Dec. 31, 2018

Selected Quarterly Financial Information [Abstract]

SELECTED QUARTERLY INFORMATION

Ameren	2018								2017
Quarter ended	March 31		June 30		September 30		December 31		March 31		June 30		September 30		December 31
Operating revenues(a)	$	1,585	$	1,563	$	1,724	$	1,419	$	1,515	$	1,537	$	1,723	$	1,399
Operating income(a)	273		385		533		166		242		387		569		212
Net income (loss)	153		240		359		69		104		194		290		(59		)	(b)
Net income (loss) attributable to Ameren common shareholders	$	151	$	239	$	357	$	68	$	102	$	193	$	288	$	(60	)
Earnings (loss) per common share – basic	$	0.62	$	0.98	$	1.46	$	0.28	$	0.42	$	0.79	$	1.19	$	(0.24	)
Earnings (loss) per common share – diluted(c)	$	0.62	$	0.97	$	1.45	$	0.28	$	0.42	$	0.79	$	1.18	$	(0.24	)

(a) 2017 amounts have been revised to reflect the adoption of accounting guidance on revenue from contracts with customers and the presentation of net periodic pension and postretirement benefit cost, effective for the Ameren Companies as of January 1, 2018. See Note 1 – Summary of Significant Accounting Policies and Note 10 – Retirement Benefits under Part II, Item 8, of this report for additional information.

(b) Includes an increase to income tax expense of $154 million recorded in 2017 as a result of the TCJA.

(c) The sum of quarterly amounts, including per share amounts, may not equal amounts reported for year-to-date periods. This is because of the effects of rounding and the changes in the number of weighted-average diluted shares outstanding each period.

Ameren Missouri Quarter ended	Operating Revenues(a)		Operating Income(a)		Net Income (Loss)				Net Income (Loss) Available to Common Shareholder
March 31, 2018	$	792	$	90	$	39			$	38
March 31, 2017	791		47		6				5
June 30, 2018	955		258		169				168
June 30, 2017	934		230		121				120
September 30, 2018	1,129		394		295				294
September 30, 2017	1,116		412		235				234
December 31, 2018	713		7		(22		)		(22		)
December 31, 2017	696		33		(36		)	(b)	(36		)

(a) 2017 amounts have been revised to reflect the adoption of accounting guidance on revenue from contracts with customers and the presentation of net periodic pension and postretirement benefit cost, effective for the Ameren Companies as of January 1, 2018. See Note 1 – Summary of Significant Accounting Policies and Note 10 – Retirement Benefits under Part II, Item 8, of this report for additional information.

(b) Includes an increase to income tax expense of $32 million recorded in 2017 as a result of the TCJA.

Ameren Illinois Quarter ended	Operating Revenues(a)		Operating Income(a)		Net Income		Net Income Available to Common Shareholder
March 31, 2018	$	760	$	159	$	96	$	95
March 31, 2017	703		169		80		79
June 30, 2018	578		105		63		62
June 30, 2017	576		128		58		57
September 30, 2018	564		113		63		63
September 30, 2017	574		124		55		55
December 31, 2018	674		135		85		84
December 31, 2017	674		148		78		77

(a) 2017 amounts have been revised to reflect the adoption of accounting guidance on revenue from contracts with customers and the presentation of net periodic pension and postretirement benefit cost, effective for the Ameren Companies as of January 1, 2018. See Note 1 – Summary of Significant Accounting Policies and Note 10 – Retirement Benefits under Part II, Item 8, of this report for additional information.