Property And Plant, Net (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Schedule Of Property And Plant, Net

The following table presents property, plant, and equipment, net, for each of the Ameren Companies at December 31, 2018 and 2017:

	Ameren Missouri(a)		Ameren Illinois		Other		Ameren(a)
2018
Property, plant, and equipment at original cost:(b)
Electric generation	$	11,432	$	—	$	—	$	11,432
Electric distribution	5,989		5,970		—		11,959
Electric transmission	1,277		2,647		1,385		5,309
Natural gas	500		2,701		—		3,201
Other(c)	1,008		863		230		2,101
	20,206		12,181		1,615		34,002
Less: Accumulated depreciation and amortization	8,726		3,294		253		12,273
	11,480		8,887		1,362		21,729
Construction work in progress:
Nuclear fuel in process	217		—		—		217
Other	406		311		147		864
Property, plant, and equipment, net	$	12,103	$	9,198	$	1,509	$	22,810
2017
Property, plant, and equipment at original cost:(b)
Electric generation	$	11,132	$	—	$	—	$	11,132
Electric distribution	5,766		5,649		—		11,415
Electric transmission	1,201		2,298		1,167		4,666
Natural gas	474		2,419		—		2,893
Other(c)	922		757		242		1,921
	19,495		11,123		1,409		32,027
Less: Accumulated depreciation and amortization	8,305		3,082		246		11,633
	11,190		8,041		1,163		20,394
Construction work in progress:
Nuclear fuel in process	148		—		—		148
Other	413		252		259		924
Property, plant, and equipment, net	$	11,751	$	8,293	$	1,422	$	21,466

(a) Amounts in Ameren and Ameren Missouri include two CTs under separate agreements. The gross cumulative asset value of those agreements was $235 million and $233 million at December 31, 2018 and 2017, respectively. The total accumulated depreciation associated with the two CTs was $89 million and $83 million at December 31, 2018 and 2017, respectively. See Note 5 – Long-term Debt and Equity Financings for additional information on these agreements.

(b) The estimated lives for each asset group are as follows: 5 to 72 years for electric generation, excluding Ameren Missouri’s hydro generating assets which have useful lives of up to 150 years, 20 to 80 years for electric distribution, 50 to 75 years for electric transmission, 20 to 80 years for natural gas, and 5 to 55 years for other.

(c) Other property, plant, and equipment includes assets used to support electric and natural gas services.

Accrued Capital Expenditures

The following table provides accrued capital and nuclear fuel expenditures at December 31, 2018, 2017, and 2016, which represent noncash investing activity excluded from the accompanying statements of cash flows:

	Ameren		Ameren Missouri		Ameren Illinois
Accrued capital expenditures:
2018	$	272	$	121	$	138
2017	361		159		175
2016	251		116		87
Accrued nuclear fuel expenditures:
2018	$	20	$	20	$	—
2017	10		10		—
2016	20		20		—

Schedule of Capitalized Software [Table Text Block]

Capitalized software costs are classified within “Property, Plant, and Equipment, Net” on the balance sheet and are amortized on a straight-line basis over the expected period of benefit, ranging from 5 to 10 years. The following table presents the amortization expense of capitalized software, the gross carrying value of capitalized software, and the related accumulated amortization by year:

	Amortization Expense(a)						Gross Carrying Value				Accumulated Amortization
	2018		2017		2016		2018		2017		2018			2017
Ameren	$	71	$	58	$	52	$	734	$	655	$	(514	)	$	(466	)
Ameren Missouri	24		20		17		223		191		(125		)	(107		)
Ameren Illinois	44		36		33		297		241		(183		)	(146		)

(a) As of December 31, 2018, the estimated amortization expense of capitalized software for each of the five succeeding years is not expected to differ materially from the current year expense.