Summary Of Significant Accounting Policies (Tables)

3 Months Ended

6 Months Ended

Jun. 30, 2018

Schedule of Cash and Cash Equivalents Including Restricted Cash

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets and the statements of cash flows as of June 30, 2018 and 2017, and December 31, 2017 and 2016:



	June 30, 2018						December 31, 2017						June 30, 2017						December 31, 2016
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
Cash and cash equivalents^(a)	$	29	$	17	$	—	$	10	$	—	$	—	$	10	$	—	$	—	$	9	$	—	$	—
Restricted cash included in “Other current assets”	12		4		6		21		5		6		19		4		5		20		4		6
Restricted cash included in “Other assets”	51		—		51		35		—		35		23		—		23		22		—		22
Restricted cash included in “Nuclear decommissioning trust fund”	4		4		(b)		2		2		(b)		1		1		(b)		1		1		(b)
Total cash, cash equivalents, and restricted cash^(c)	$	96	$	25	$	57	$	68	$	7	$	41	$	53	$	5	$	28	$	52	$	5	$	28


(a)	As presented on the balance sheet.


(b)	Not applicable.


(c)	As presented on the statement of cash flows.

Schedule of Cash Flow, Supplemental Disclosures

The following table provides noncash investing activity excluded from the statements of cash flows for the six months ended June 30, 2018 and 2017:



	June 30, 2018						June 30, 2017
	Ameren^(a)		Ameren Missouri		Ameren Illinois		Ameren^(a)		Ameren Missouri		Ameren Illinois
Accrued capital expenditures	$	233	$	80	$	147	$	175	$	61	$	79
Net realized and unrealized gain – nuclear decommissioning trust fund	1		1		(b)		36		36		(b)


(a)	Includes amounts for Ameren registrant and nonregistrant subsidiaries.


(b)	Not applicable.

Asset Retirement Obligation Disclosure

The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the six months ended June 30, 2018:



	Ameren Missouri				Ameren Illinois^(a)		Ameren
Balance at December 31, 2017	$	640		^(b)	$	4	$	644		^(b)
Liabilities settled	(2		)		(c)		(2		)
Accretion^(d)	14				(c)		14
Change in estimates^(e)	(9		)		—		(9		)
Balance at June 30, 2018	$	643		^(b)	$	4	$	647		^(b)


(a)	Included in “Other deferred credits and liabilities” on the balance sheet.


(b)	Balance included $6 million in “Other current liabilities” on the balance sheet as of both December 31, 2017, and June 30, 2018, respectively.


(c)	Less than $1 million.


(d)	Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.


(e)	Ameren Missouri changed its fair value estimate primarily due to a reduction in the cost estimate for closure of certain CCR storage facilities

Summary Of Nonvested Shares Related To Long-Term Incentive Plan

six months ended June 30, 2018:



	Performance Share Units				Restricted Stock Units
	Share Units		Weighted-average Fair Value per Share Unit		Stock Units		Weighted-average Fair Value per Stock Unit
Nonvested at January 1, 2018^(a)	895,489		$	52.28	—		$	—
Granted	306,252		62.88		184,351		57.60
Forfeitures	(54,213	)	49.72		(3,560	)	58.99
Undistributed vested units^(b)	(145,169	)	53.50		(12,983	)	58.98
Vested and distributed	(176,043	)	52.88		—		—
Nonvested at June 30, 2018^(c)	826,316		$	56.03	167,808		$	57.46


(a)	Does not include 712,572 undistributed vested performance share units.


(b)	Undistributed vested units are awards that vested due to attainment of retirement eligibility by certain employees, but have not yet been distributed. For undistributed vested performance share units, the number of shares issued for retirement-eligible employees will vary depending on actual performance over the three-year performance period.


(c)	Does not include 476,361 undistributed vested performance share units and 12,983 undistributed vested restricted stock units.

Schedule of Excise Taxes

The following table presents the excise taxes recorded in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” for the three and six months ended June 30, 2018 and 2017:



	Three Months					Six Months
	2018		2017			2018		2017
Ameren Missouri	$	46	$	40		$	80	$	71
Ameren Illinois	28		23		^(a)	63		57		^(a)
Ameren	$	74	$	63	^(a)	$	143	$	128	^(a)


(a)	Amounts have been adjusted from those previously reported to reflect additional excise taxes for the three and six months ended June 30, 2017, respectively.

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three and six months ended June 30, 2018 and 2017:



	Ameren		Ameren Missouri			Ameren Illinois
Three Months	2018	2017	2018		2017	2018	2017
Federal statutory corporate income tax rate:	21%	35%	21%		35%	21%	35%
Increases (decreases) from:
Amortization of excess deferred taxes	(1)	—	—	^(a)	—	(5)	—
Other depreciation differences	—	—	—		—	(1)	(1)
Amortization of deferred investment tax credit	—	—	(1)		(1)	—	—
State tax	5	4	4		3	8	5
Tax credits	(1)	—	—		—	—	—
Other permanent items	—	(1)	—		—	—	—
Effective income tax rate	24%	38%	24%		37%	23%	39%
Six Months
Federal statutory corporate income tax rate:	21%	35%	21%		35%	21%	35%
Increases (decreases) from:
Amortization of excess deferred taxes	(2)	—	—	^(a)	—	(4)	—
Amortization of deferred investment tax credit	(1)	(1)	(1)		(1)	—	—
State tax	6	5	4		3	7	5
Other permanent items	(1)	(2)	—		—	—	(1)
Effective income tax rate	23%	37%	24%		37%	24%	39%


(a)	Based on an order issued by the MoPSC in July 2018, Ameren Missouri began amortizing excess deferred taxes in August 2018. See Note 2 – Rate and Regulatory Matters for additional information.