American Water Works (AWK) 10-K 25 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 19, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	AWK
Entity Registrant Name	American Water Works Company, Inc.
Entity Central Index Key	1,410,636
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		178,008,765
Entity Public Float			$ 7,839,400,000

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Property, plant and equipment	$ 18,504	$ 17,269
Accumulated depreciation	(4,571)	(4,240)
Property, plant and equipment, net	13,933	13,029
Current assets:
Cash and cash equivalents	45	23
Restricted funds	21	14
Accounts receivable, net	255	232
Unbilled revenues	267	221
Materials and supplies	38	37
Other	31	48
Total current assets	657	575
Regulatory and other long-term assets:
Regulatory assets	1,271	1,153
Goodwill	1,302	1,208
Other	78	73
Total regulatory and other long-term assets	2,651	2,434
TOTAL ASSETS	17,241	16,038	[1]
Capitalization:
Common stock ($0.01 par value, 500,000,000 shares authorized, 180,907,483 and 179,461,606 shares issued as of December 31, 2015 and 2014, respectively)	2	2
Paid-in-capital	6,351	6,302
Accumulated deficit	(1,073)	(1,296)
Accumulated other comprehensive loss	(88)	(82)
Treasury stock, at cost (2,625,112 and 260,243 shares as of December 31, 2015 and 2014, respectively)	(143)	(11)
Total common stockholders' equity	5,049	4,915
Long-term debt
Long-term debt	5,862	5,427
Redeemable preferred stock at redemption value	12	15
Total capitalization	10,923	10,357
Current liabilities:
Short-term debt	628	450
Current portion of long-term debt	54	61
Accounts payable	126	100
Accrued liabilities	493	395
Taxes accrued	26	25
Interest accrued	62	57
Other	144	153
Total current liabilities	1,533	1,241
Regulatory and other long-term liabilities:
Advances for construction	349	368
Deferred income taxes, net	2,310	2,034
Deferred investment tax credits	24	25
Regulatory liabilities	402	392
Accrued pension	342	316
Accrued postretirement benefit	169	193
Other	68	37
Total regulatory and other long-term liabilities	3,664	3,365
Contributions in aid of construction	$ 1,121	$ 1,075
Commitments and contingencies (See Note 15)
TOTAL CAPITALIZATION AND LIABILITIES	$ 17,241	$ 16,038
[1]	The information has been revised to reflect the retrospective application of ASU 2015-15 Presentation of Debt Issuance Costs and ASU 2015-17 Income Taxes. See Note 2–Significant Accounting Policies for additional details.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	180,907,483	179,461,606
Treasury Stock, shares	2,625,112	260,243

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Operating revenues		$ 3,159	$ 3,011	$ 2,879	[1]
Operating expenses:
Operation and maintenance		1,404	1,350	1,289
Depreciation and amortization		440	424	407	[1]
General taxes		243	236	234
(Gain) loss on asset dispositions and purchases		(3)	(2)	1
Total operating expenses, net		2,084	2,008	1,931	[1]
Operating income		1,075	1,003	948
Other income (expenses):
Interest, net		(308)	(299)	(308)
Loss on extinguishment of debt				(41)
Other, net		15	6	9
Total other income (expenses)		(293)	(293)	(340)
Income from continuing operations before income taxes		782	710	608	[1]
Provision for income taxes		306	280	237
Income from continuing operations		476	430	371
Loss from discontinued operations, net of tax			(7)	(2)
Net income attributable to common stockholders		$ 476	$ 423	$ 369
Basic earnings per share:
Income from continuing operations	[2]	$ 2.66	$ 2.40	$ 2.08
Loss from discontinued operations, net of tax	[2]		(0.04)	(0.01)
Net income attributable to common stockholders	[2]	2.66	2.36	2.08
Diluted earnings per share:
Income from continuing operations	[2]	2.64	2.39	2.07
Loss from discontinued operations, net of tax	[2]		(0.04)	(0.01)
Net income attributable to common stockholders	[2]	$ 2.64	$ 2.35	$ 2.06
Weighted average common shares outstanding
Basic		179	179	178
Diluted		180	180	179
Dividends declared per common share		$ 1.36	$ 1.24	$ 1.12
[1]	The information has been revised to reflect the impact of discontinued operations, as applicable. See Note 3—Acquisitions and Divestitures for additional details on the Company’s discontinued operations.
[2]	Amounts may not sum due to rounding.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income attributable to common stockholders	$ 476	$ 423	$ 369
Other comprehensive (loss) income, net of tax:
Change in employee benefit plan funded status, net of tax of $(6), $(29) and $47 in 2015, 2014 and 2013, respectively	(10)	(46)	73
Pension amortized to periodic benefit cost:
Actuarial loss, net of tax of $3 and $6 in 2015 and 2013, respectively	5		9
Foreign currency translation adjustment	(1)		(1)
Unrealized loss on cash flow hedge, net of tax of $(1)		(1)
Other comprehensive (loss) income	(6)	(47)	81
Comprehensive income attributable to common stockholders	$ 470	$ 376	$ 450

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Change in employee benefit plan funded status, tax	$ (6)	$ (29)	$ 47
Actuarial loss, tax	$ 3		$ 6
Unrealized loss on cash flow hedge, tax		$ (1)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 476	$ 423	$ 369
Adjustments to reconcile to net cash flows provided by operating activities:
Depreciation and amortization	440	424	407
Deferred income taxes and amortization of investment tax credits	296	254	250
Provision for losses on accounts receivable	32	37	27
(Gain) loss on asset dispositions and purchases	(3)	(2)	1
Pension and non-pension postretirement benefits	61	24	78
Other non-cash, net	(53)	(14)	(1)
Changes in assets and liabilities:
Receivables and unbilled revenues	(84)	(62)	(79)
Pension and non-pension postretirement benefit contributions	(57)	(52)	(98)
Accounts payable and accrued liabilities	80	27	15
Other current assets and liabilities, net	(9)	38	(73)
Net cash provided by operating activities	1,179	1,097	896
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(1,160)	(956)	(980)
Acquisitions	(197)	(9)	(24)
Proceeds from sale of assets and securities	5	14	1
Removal costs from property, plant and equipment retirements, net	(107)	(78)	(65)
Net funds (restricted) released	(6)	15	15
Net cash used in investing activities	(1,465)	(1,014)	(1,053)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	565	501	404
Repayments of long-term debt	(130)	(240)	(496)
Proceeds from short-term borrowings with maturities greater than three months	60	35	221
Repayments of short-term borrowings with maturities greater than three months	(60)	(256)
Net short-term borrowings with maturities less than three months	180	41	139
Proceeds from issuances of employee stock plans and DRIP	39	21	26
Advances and contributions for construction, net of refunds of $23, $21 and $23 in 2015, 2014 and 2013, respectively	26	26	19
Debt issuance costs	(7)	(5)	(4)
Dividends paid	(239)	(216)	(149)
Anti-dilutive share repurchases	(126)
Tax benefit realized from equity compensation		6
Net cash provided by (used in) financing activities	308	(87)	160
Net increase (decrease) in cash and cash equivalents	22	(4)	3
Cash and cash equivalents at beginning of period	23	27	24
Cash and cash equivalents at end of period	45	23	27
Cash paid during the year for:
Interest, net of capitalized amount	309	301	318
Income taxes, net of refunds of $1 and $4 in 2015 and 2014, respectively	12	16	8
Non-cash investing activity:
Capital expenditures acquired on account but unpaid as of year end	$ 224	$ 186	$ 129

Consolidated Statements of Cas8

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Cash Flows [Abstract]
Advances and contributions for construction, refunds	$ 23	$ 21	$ 23
Income taxes, refunds	$ 1	$ 4	$ 4

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Treasury Stock	Preferred Stock of Subsidiary Companies Without Mandatory Redemption Requirements
Beginning Balance at Dec. 31, 2012	$ 4,445	$ 2	$ 6,223	$ (1,665)	$ (116)		$ 1
Beginning Balance (in shares) at Dec. 31, 2012		177,000,000
Net income attributable to common stockholders	369			369
Direct stock reinvestment and purchase plan	2		2
Direct stock reinvestment and purchase plan (in shares)		100,000
Employee stock purchase plan	5		5
Employee stock purchase plan (in shares)		100,000
Stock-based compensation activity	26		32	(1)		$ (5)
Stock-based compensation activity (in shares)		1,200,000				(100,000)
Subsidiary preferred stock redemption	(1)						$ (1)
Other comprehensive income (loss), net of tax	81				81
Dividends	(199)			(199)
Ending Balance at Dec. 31, 2013	4,728	$ 2	6,262	(1,496)	(35)	$ (5)
Ending Balance (in shares) at Dec. 31, 2013		178,400,000				(100,000)
Net income attributable to common stockholders	423			423
Direct stock reinvestment and purchase plan	2		2
Direct stock reinvestment and purchase plan (in shares)		100,000
Employee stock purchase plan	5		5
Employee stock purchase plan (in shares)		100,000
Stock-based compensation activity	26		33	(1)		$ (6)
Stock-based compensation activity (in shares)		900,000				(100,000)
Other comprehensive income (loss), net of tax	(47)				(47)
Dividends	(222)			(222)
Ending Balance at Dec. 31, 2014	$ 4,915	$ 2	6,302	(1,296)	(82)	$ (11)
Ending Balance (in shares) at Dec. 31, 2014		179,500,000				(200,000)
Beginning Balance (in shares) at Dec. 31, 2014	(260,243)
Cumulative effect of change in accounting principle	$ (8)			(8)
Net income attributable to common stockholders	476			476
Direct stock reinvestment and purchase plan	4		4
Direct stock reinvestment and purchase plan (in shares)		100,000
Employee stock purchase plan	5		5
Employee stock purchase plan (in shares)		100,000
Stock-based compensation activity	33		40	(1)		$ (6)
Stock-based compensation activity (in shares)		1,200,000				(100,000)
Repurchases of common stock	$ (126)					$ (126)
Repurchases of common stock (in shares)	(2,300,000)					(2,300,000)
Other comprehensive income (loss), net of tax	$ (6)				(6)
Dividends	(244)			(244)
Ending Balance at Dec. 31, 2015	$ 5,049	$ 2	$ 6,351	$ (1,073)	$ (88)	$ (143)
Ending Balance (in shares) at Dec. 31, 2015		180,900,000				(2,600,000)

Consolidated Statements of Ch10

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Stockholders Equity [Abstract]
Other comprehensive income (loss), tax	$ (3)	$ (30)	$ 53

Organization and Operation

Organization and Operation	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Operation	Note 1: Organization and Operation American Water Works Company, Inc. (the “Company” or “American Water”) is the holding company for regulated and market-based subsidiaries throughout the United States of America and Ontario, Canada. The Regulated Businesses provide water and wastewater services as public utilities in 16 states in the United States. The Market-Based Businesses is comprised of four non-reportable operating segments including Military Services Group, which conducts operation and maintenance (“O&M”) of water and wastewater systems for military bases; Contract Operations Group, which conducts operation and maintenance of water and wastewater facilities for municipalities and the food and beverage industry; Homeowner Services Group, which primarily provides water and sewer line protection plans for homeowners; and Keystone Operations, which provides water services for natural gas exploration and production companies.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2: Significant Accounting Policies Principles of Consolidation The accompanying consolidated financial statements include the accounts of American Water and all of its subsidiaries in which a controlling interest is maintained after the elimination of intercompany accounts and transactions. Intercompany balances and transactions between subsidiaries have been eliminated. The Company uses the equity method to report its investments in joint ventures in which the Company holds up to a 50% voting interest and cannot exercise control over the operations and policies of the investments. Under the equity method, the Company records its interests as an investment and its percentage share of the investee’s earnings as earnings or losses. In July 2015, the Company acquired a ninety-five percent interest in Water Solutions Holdings, LLC, including its wholly-owned subsidiary, Keystone Clearwater Solutions, LLC (collectively referred to as “Keystone”). The outside stockholders’ interest, which is redeemable at the option of the minority owners, is recognized as redeemable noncontrolling interest. The redeemable noncontrolling interest amounted to $7 as of December 31, 2015 and is included in other long-term liabilities in the accompanying Consolidated Balance Sheets. The net loss attributable to the noncontrolling interest was not significant. The Company has entered into an agreement, whereby it has the option to acquire from the minority owners, and the minority owners have the option to sell to the Company, the remaining five percent interest at fair value upon the occurrence of certain triggering events or at defined dates of December 31, 2016 and December 31, 2018. Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates. The Company considers its critical accounting estimates to include: the application of regulatory accounting principles and the related determination and estimates of regulatory assets and liabilities; estimates used in impairment testing of goodwill and other long-lived assets, including regulatory assets; revenue recognition; accounting for income taxes; benefit plan assumptions; and contingent liabilities. The Company’s critical accounting estimates that are particularly sensitive to change in the near term are amounts reported for regulatory assets and liabilities, benefit plans assumptions, contingency-related obligations and goodwill. Regulation The Company’s regulated utilities are subject to economic regulation by the public utility commissions and the local governments of the states in which they operate (the “PUCs”). These PUCs generally authorize revenue at levels intended to recover the estimated costs of providing service, plus a return on net investments, or rate base. Regulators may also impose certain penalties or grant certain incentives. Due to timing and other differences in the collection of utility revenue, an incurred cost that would otherwise be charged to expense by a non-regulated entity is to be deferred as a regulatory asset if it is probable that the cost is recoverable in future rates. Conversely, GAAP requires recording of a regulatory liability for amounts collected in rates to recover costs expected to be incurred in the future or amounts collected in excess of costs incurred and refundable to customers. See Note 6—Regulatory Assets and Liabilities. Property, Plant and Equipment Property, plant and equipment consist primarily of utility plant. Additions to utility plant and replacements of retirement units of property are capitalized. Costs include material, direct labor and such indirect items as engineering and supervision, payroll taxes and benefits, transportation and an allowance for funds used during construction (“AFUDC”). The cost of repairs, maintenance, including planned major maintenance activities, and minor replacements is charged to maintenance expense as incurred. The costs incurred to acquire and internally develop computer software for internal use are capitalized as a unit of property. The carrying value of these costs amounted to $311 and $320 as of December 31, 2015 and 2014, respectively. When units of property are replaced, retired or abandoned, the recorded value is credited to the asset account and charged to accumulated depreciation. To the extent the Company recovers cost of removal or other retirement costs through rates after the retirement costs are incurred, a regulatory asset is recorded. In some cases, the Company recovers retirement costs through rates during the life of the associated asset and before the costs are incurred. These amounts result in a regulatory liability being reported based on the amounts previously recovered through customer rates, until the costs to retire those assets are incurred. The cost of property, plant and equipment is depreciated using the straight-line average remaining life method. The Company’s regulated utility subsidiaries record depreciation in conformity with amounts approved by state regulators after regulatory review of information the Company submits to support its estimates of the assets’ remaining useful lives. Nonutility property consists primarily of buildings and equipment utilized by the Company for internal operations. This property is stated at cost, net of accumulated depreciation calculated using the straight-line method over the useful lives of the assets. Cash and Cash Equivalents Substantially all cash is invested in interest-bearing accounts. All highly liquid investments with a maturity of three months or less when purchased are considered to be cash equivalents. Restricted Funds Restricted funds primarily represent proceeds from financings for the construction and capital improvement of facilities and deposits for future services under operation and maintenance projects. The proceeds from these financings are held in escrow until the designated expenditures are incurred. Classification of restricted funds in the Consolidated Balance Sheets as either current or long-term is based upon the intended use of the funds. Accounts Receivable and Unbilled Revenues Accounts receivable include regulated utility customer accounts receivable, which represent amounts billed to water and wastewater customers on a cycle basis. Credit is extended based on the guidelines of the applicable PUCs and collateral is generally not required. Also included are market-based trade accounts receivable and nonutility customer receivables of the regulated subsidiaries. Unbilled revenues are accrued when service has been provided but has not been billed to customers. Allowance for Uncollectible Accounts Allowances for uncollectible accounts are maintained for estimated probable losses resulting from the Company’s inability to collect receivables from customers. Accounts that are outstanding longer than the payment terms are considered past due. A number of factors are considered in determining the allowance for uncollectible accounts, including the length of time receivables are past due and previous loss history. The Company generally writes off accounts when they become uncollectible or are over a certain number of days outstanding. See Note 5—Allowance for Uncollectible Accounts. Materials and Supplies Materials and supplies are stated at the lower of cost or net realizable value. Cost is determined using the average cost method. Goodwill Goodwill represents the excess of the purchase price paid over the estimated fair value of the assets acquired and liabilities assumed in the acquisition of a business. Goodwill is not amortized, but is tested for impairment at least annually or on an interim basis if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying value. Goodwill is primarily associated with the acquisitions of E’town Corporation in 2001, American Water in 2003 and Keystone in 2015 (the “Acquisitions”) and has been assigned to reporting units based on the fair values at the date of the Acquisitions. The reporting units in the Regulated Businesses segment are aggregated into a single reporting unit. The Market-Based Businesses is comprised of four non-reportable operating segments. The Company’s annual impairment test is performed as of November 30 of each year, in conjunction with the completion of the Company’s annual business plan. The Company assesses qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. If based on qualitative factors, the fair value of the reporting unit is more likely than not greater than the carrying amount, no further testing is required. If the Company bypasses the qualitative assessment or performs the qualitative assessment, but determines that it is more likely than not that its fair value is less than its carrying amount, a quantitative two-step, fair value-based test is performed. The first step compares the estimated fair value of the reporting unit to its respective net carrying value, including goodwill, on the measurement date. If the estimated fair value of any reporting unit is less than such reporting unit’s carrying value, then the second step is performed to measure the amount of the impairment loss (if any) for such reporting unit. The second step requires an allocation of fair value to the individual assets and liabilities using purchase price allocation accounting guidance in order to determine the implied fair value of goodwill. If the implied fair value of goodwill is less than the carrying amount for the reporting unit, an impairment loss is recorded as a reduction to goodwill and a charge to operating expense. Application of the goodwill impairment test requires management judgment, including the identification of reporting units and determining the fair value of the reporting unit. Management estimates fair value using a combination of a discounted cash flow analysis and market multiples analysis. Significant assumptions used in these fair value analyses include discount and growth rates and projected terminal values. The Company believes the assumptions and other considerations used to value goodwill to be appropriate. However, if experience differs from the assumptions and considerations used in its analysis, the resulting change could have a material adverse impact on the consolidated financial statements. Long-Lived Assets Long-lived assets include land, buildings, equipment and long-term investments. Long-lived assets, other than investments and land, are depreciated over their estimated useful lives, and are reviewed for impairment whenever changes in circumstances indicate the carrying value of the asset may not be recoverable. Such circumstances would include items such as a significant decrease in the market value of a long-lived asset, a significant adverse change in the manner the asset is being used or planned to be used or in its physical condition, or a history of operating or cash flow losses associated with the use of the asset. In addition, changes in the expected useful life of these long-lived assets may also be an impairment indicator. When such events or changes occur, the Company estimates the fair value of the asset from future cash flows expected to result from the use and, if applicable, the eventual disposition of the asset and compares that to the carrying value of the asset. If the carrying value is greater than the fair value, an impairment loss is recorded. The Company believes the assumptions and other considerations used to evaluate the carrying value of long-lived assets are appropriate. However, if actual experience differs from the assumptions and considerations used in its estimates, the resulting change could have a material adverse impact on the consolidated financial statements. The key variables to determine fair value include assumptions regarding sales volume, rates, operating costs, labor and other benefit costs, capital additions, assumed discount rates and other economic factors. These variables require significant management judgment and include inherent uncertainties, since they are forecasting future events. If such assets are considered impaired, an impairment loss is recognized equal to the amount by which the asset’s carrying value exceeds its fair value. The long-lived assets of the regulated utility subsidiaries are tested on a separate entity basis for impairment testing as they are integrated state-wide operations that do not have the option to curtail service and generally have uniform tariffs. A regulatory asset is charged to earnings if and when future recovery in rates of that asset is no longer probable. The Company holds other investments including investments in privately held companies and investments in joint ventures accounted for using the equity method. The Company’s investments in privately held companies and joint ventures are classified as other long-term assets in the accompanying Consolidated Balance Sheets. The fair values of long-term investments are dependent on the financial performance and solvency of the entities in which the Company invests, as well as volatility inherent in the external markets. If such assets are considered impaired, an impairment loss is recognized equal to the amount by which the asset’s carrying value exceeds its fair value. Advances for Construction and Contributions in Aid of Construction Regulated utility subsidiaries may receive advances for construction and contributions in aid of construction from customers, home builders and real estate developers to fund construction necessary to extend service to new areas. Advances are refundable for limited periods of time as new customers begin to receive service or other contractual obligations are fulfilled. Included in other current liabilities as of December 31, 2015 and 2014 in the accompanying Consolidated Balance Sheets are estimated refunds of $19 and $18, respectively. Those amounts represent expected refunds during the next 12-month period. Advances that are no longer refundable are reclassified to contributions. Contributions are permanent collections of plant assets or cash for a particular construction project. For ratemaking purposes, the amount of such contributions generally serves as a rate base reduction since the contributions represent non-investor supplied funds. Generally, the Company depreciates utility plant funded by contributions and amortizes its contributions balance as a reduction to depreciation expense, producing a result which is functionally equivalent to reducing the original cost of the utility plant for the contributions. In accordance with applicable regulatory guidelines, some of the Company’s utility subsidiaries do not amortize contributions, and any contribution received remains on the balance sheet indefinitely. Amortization of contributions in aid of construction was $26, $24 and $22 for the years ended December 31, 2015, 2014 and 2013, respectively. Recognition of Revenues Revenues of the regulated utility subsidiaries are recognized as water and wastewater services are provided, and include amounts billed to customers on a cycle basis and unbilled amounts based on estimated usage from the date of the meter reading associated with the latest customer bill to the end of the accounting period. The Company has agreements with the U.S. Department of Defense to operate and maintain water and wastewater systems at various military bases pursuant to 50-year contracts (“military agreements”). These contracts also include construction components that are accounted for separately from the O&M components. Nine of the military agreements are subject to periodic price redetermination adjustments and modifications for changes in circumstance. The remaining three agreements are subject to annual price adjustments under a mechanism similar to price redeterminations. Additionally, the Company has agreements ranging in length from two to 40 years with municipalities and businesses in various industries to operate and maintain water and wastewater systems (“O&M agreements”). Revenues from operations and management services are recognized as services are provided. See Note 15—Commitments and Contingencies. Revenues from construction projects are recognized over the contract term based on the costs incurred to date during the period compared to the total estimated costs over the entire contract. Losses on contracts are recognized during the period in which the loss first becomes probable and estimable. Revenues recognized during the period in excess of billings on construction contracts are recorded as unbilled revenue. Billings in excess of revenues recognized on construction contracts are recorded as other current liabilities until the recognition criteria are met. Changes in contract performance and related estimated contract profitability may result in revisions to costs and revenues and are recognized in the period in which revisions are determined. Income Taxes American Water and its subsidiaries participate in a consolidated federal income tax return for U.S. tax purposes. Members of the consolidated group are charged with the amount of federal income tax expense determined as if they filed separate returns. Certain income and expense items are accounted for in different time periods for financial reporting than for income tax reporting purposes. The Company provides deferred income taxes on the difference between the tax basis of assets and liabilities and the amounts at which they are carried in the financial statements. These deferred income taxes are based on the enacted tax rates expected to be in effect when these temporary differences are projected to reverse. In addition, the regulated utility subsidiaries recognize regulatory assets and liabilities for the effect on revenues expected to be realized as the tax effects of temporary differences, previously flowed through to customers, reverse. Investment tax credits have been deferred by the regulated utility subsidiaries and are being amortized to income over the average estimated service lives of the related assets. The Company recognizes accrued interest and penalties related to tax positions as a component of income tax expense and accounts for sales tax collected from customers and remitted to taxing authorities on a net basis. Allowance for Funds Used During Construction AFUDC is a non-cash credit to income with a corresponding charge to utility plant that represents the cost of borrowed funds or a return on equity funds devoted to plant under construction. The regulated utility subsidiaries record AFUDC to the extent permitted by the PUCs. The portion of AFUDC attributable to borrowed funds is shown as a reduction of interest, net in the accompanying Consolidated Statements of Operations. Any portion of AFUDC attributable to equity funds would be included in other income (expenses) in the accompanying Consolidated Statements of Operations. AFUDC is summarized in the following table for the years ended December 31: 2015 2014 2013 Allowance for other funds used during construction $ 13 $ 9 $ 13 Allowance for borrowed funds used during construction 8 6 6 Environmental Costs The Company’s water and wastewater operations are subject to U.S. federal, state, local and foreign requirements relating to environmental protection, and as such, the Company periodically becomes subject to environmental claims in the normal course of business. Environmental expenditures that relate to current operations or provide a future benefit are expensed or capitalized as appropriate. Remediation costs that relate to an existing condition caused by past operations are accrued, on an undiscounted basis, when it is probable that these costs will be incurred and can be reasonably estimated. Remediation costs accrued amounted to $1 and $2 as of December 31, 2015 and 2014, respectively. The accrual relates entirely to a conservation agreement entered into by a subsidiary of the Company with the National Oceanic and Atmospheric Administration (“NOAA”) requiring the Company to, among other provisions, implement certain measures to protect the steelhead trout and its habitat in the Carmel River watershed in the State of California. The Company has agreed to pay $1 annually from 2010 to 2016. The Company’s inception-to-date costs related to the NOAA agreement were recorded in regulatory assets in the accompanying Consolidated Balance Sheets as of December 31, 2015 and 2014 and are expected to be fully recovered from customers in future rates. Derivative Financial Instruments The Company uses derivative financial instruments for purposes of hedging exposures to fluctuations in interest rates. These derivative contracts are entered into for periods consistent with the related underlying exposures and do not constitute positions independent of those exposures. The Company does not enter into derivative contracts for speculative purposes and does not use leveraged instruments. All derivatives are recognized on the balance sheet at fair value. On the date the derivative contract is entered into, the Company may designate the derivative as a hedge of the fair value of a recognized asset or liability (fair-value hedge) or a hedge of a forecasted transaction or of the variability of cash flows to be received or paid related to a recognized asset or liability (cash-flow hedge). Changes in the fair value of a fair-value hedge, along with the gain or loss on the underlying hedged item, are recorded in current-period earnings. The effective portion of gains and losses on cash-flow hedges are recorded in other comprehensive income, until earnings are affected by the variability of cash flows. Any ineffective portion of designated hedges is recognized in current-period earnings. Cash flows from derivative contracts are included in net cash provided by operating activities in the accompanying Consolidated Statements of Cash Flows. New Accounting Standards The following recently issued accounting standards have been adopted by the Company as of December 31, 2015: Standard Description Date of Adoption Application Effect on the Consolidated Financial Statements (or Other Significant Matters) Service Concession Arrangements Clarified that an operating entity should not account for a services concession arrangement with a public-sector grantor as a lease if: (1) the grantor controls or has the ability to modify or approve the services the operating entity must provide, to whom it must provide them, and at what price; and (2) the grantor controls any residual interest in the infrastructure at the end of the arrangement. In addition, the infrastructure used in a service concession arrangement would not be recognized as property, plant and equipment of the operating entity. January 1, 2015 Modified retrospective basis The Company reduced nonutility property and other long-term assets for infrastructure related to service concession arrangements and recognized a cumulative effect adjustment of $8 net of tax, to the opening balance of accumulated deficit at January 1, 2015. Reporting Discontinued Operations Amended the criteria for determining which disposals can be presented as discontinued operations and modified related disclosure requirements. Now, a discontinued operation is defined as a component or group of components that is disposed of or is classified as held for sale and represents a strategic shift that has or will have a major effect on an entity’s operations and financial results. In addition, the update no longer precludes presentation as a discontinued operation if there are operations and cash flows of the component that have not been eliminated from the reporting entity’s ongoing operations or if there is significant continuing involvement with a component after its disposal. January 1, 2015 Prospective basis The adoption of this standard did not impact the Company’s results of operations, financial position or cash flows. Presentation of Debt Issuance Costs Updated guidance on the imputation of interest and simplified the presentation of debt issuance costs. The updated guidance requires that debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the related liability. Such treatment is consistent with the current presentation of debt discounts or premiums. October 1, 2015 Retrospective basis The December 31, 2014 Consolidated Balance Sheet was revised, which resulted in decreases of $7 to other assets and long-term debt, respectively. Unamortized debt issuance costs of $7 were included in long-term debt as of December 31, 2015. Presentation of Deferred Income Taxes Simplified the presentation of deferred income taxes and requires that deferred income tax assets and liabilities be classified as noncurrent in the balance sheet. October 1, 2015 Retrospective basis The December 31, 2014 Consolidated Balance Sheet was revised, which resulted in decreases of $87 to the current deferred income tax asset and long-term deferred income tax liability. The following recently issued accounting standards have not yet been adopted by the Company as of December 31, 2015: Standard Description Effective Date Application Effect on the Consolidated Financial Statements (or Other Significant Matters) Revenue from Contracts with Customers Provided new revenue recognition guidance that will replace most existing revenue recognition guidance in GAAP, including industry-specific guidance. Upon adoption, a company will recognize revenue for the transfer of goods or services to customers equal to the amount that it expects to be entitled to receive for those goods or services. The guidance also requires additional disclosures about the nature, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments. January 1, 2018 The Company is currently evaluating the alternative methods available and has not yet selected a transition method. The Company is currently evaluating the effect on the financial statements and related disclosures. Accounting for Fees Paid in a Cloud Computing Arrangement Clarified guidance on how customers should account for fees paid in a cloud computing arrangement. Under the new guidance, if a cloud computing arrangement contains a software license, the customer would account for the software license element of the arrangement consistent with the acquisition of other software licenses. If the cloud computing arrangement does not include a software license, the customer would account for the arrangement as a service contract. January 1, 2016 Prospective basis The effect on the financial statements upon adoption will be dependent on the software license arrangements entered into by the Company subsequent adoption. Reclassifications Certain reclassifications have been made to prior periods in the accompanying consolidated financial statements and notes to conform to the current presentation

Acquisitions and Divestitures

Acquisitions and Divestitures	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions and Divestitures	Note 3: Acquisitions and Divestitures Acquisitions During 2015, the Company closed on fourteen acquisitions of various regulated water and wastewater systems for a total aggregate purchase price of $64. Assets acquired, principally utility plant, totaled $90. Liabilities assumed totaled $26, including $10 of contributions in aid of construction, and assumed debt of $1. The Company recorded additional goodwill of $3 associated with four of its acquisitions, which is reported in its Regulated Businesses segment and is expected to be fully deductible for tax purposes. The Company also recognized a bargain purchase gain of $3 associated with five of its acquisitions, of which $1 was deferred as a regulatory liability. The Company also closed on the Keystone acquisition, which is included as part of the Market-Based Businesses, for a total purchase price of $133, net of cash received. The fair value of identifiable assets acquired and liabilities assumed was $56 and $7, respectively, and principally included the acquisition of nonutility property of $25, accounts receivable and unbilled revenues of $18 and intangible assets of $12. The purchase price allocation, which is based on the estimated fair value of net assets acquired, resulted in the Company recording redeemable noncontrolling interest of $7 and additional goodwill of $91. Goodwill is expected to be fully deductible for tax purposes. The pro forma impact of this acquisition would not have been material to the Company’s results of operations for the years ended December 31, 2015 and 2014 respectively. During 2014, the Company closed on thirteen acquisitions of various regulated water and wastewater systems for a total aggregate purchase price of $9. Assets acquired, principally plant, totaled $17. Liabilities assumed totaled $8, including $5 of contributions in aid of construction and assumed debt of $2. During 2013, the Company closed on fifteen acquisitions of various regulated water and wastewater systems for a total aggregate net purchase price of $24. Assets acquired, primarily utility plant, totaled $67. Liabilities assumed totaled $43, including $26 of contributions in aid of construction and assumed debt of $13. Included in these totals was the Company’s November 14, 2013 acquisition of all of the capital stock of Dale Service Corporation (“Dale”), a regulated wastewater utility company, for a total cash purchase price of $5 (net of cash acquired of $7), plus assumed liabilities. The Dale acquisition was accounted for as a business combination; accordingly, operating results from November 14, 2013 were included in the Company’s results of operations. The purchase price was allocated to the net tangible and intangible assets based upon their estimated fair values at the date of acquisition. The Company’s regulatory practice was followed whereby property, plant and equipment (rate base) was considered fair value for business combination purposes. Similarly, regulatory assets and liabilities acquired were recorded at book value and are subject to regulatory approval where applicable. The acquired debt was valued in a manner consistent with the Company’s Level 3 debt. See Note 17—Fair Value of Financial Instruments. Non-cash assets acquired in the Dale acquisition, primarily utility plant, totaled $41; liabilities assumed totaled $36, including debt assumed of $13 and contributions of $19. Divestitures In November 2014, the Company completed the sale of Terratec, previously included in the Market-Based Businesses. After post-close adjustments, net proceeds from the sale totaled $1, and the Company recorded a pretax loss on sale of $1. The following table summarizes the operating results of discontinued operations presented in the accompanying Consolidated Statements of Operations for the years ended December 31: 2014 2013 Operating revenues $ 13 $ 23 Total operating expenses, net 19 26 Loss from discontinued operations before income taxes (6 ) (3 ) Provision (benefit) for income taxes 1 (1 ) Loss from discontinued operations, net of tax $ (7 ) $ (2 ) The provision for income taxes of discontinued operations includes the recognition of tax expense related to the difference between the tax basis and book basis of assets upon the sales of Terratec that resulted in taxable gains, since an election was made under Section 338(h)(10) of the Internal Revenue Code to treat the sales as asset sales. There were no assets or liabilities of discontinued operations in the accompanying Consolidated Balance Sheets as of December 31, 2015 and 2014.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	Note 4: Property, Plant and Equipment The following table summarizes the major classes of property, plant and equipment by category as of December 31: Range of Remaining Weighted Average 2015 2014 Useful Lives Useful Life Utility plant: Land and other non-depreciable assets $ 141 $ 137 Sources of supply 705 681 12 to 127 Years 51 Years Treatment and pumping facilities 3,070 2,969 3 to 101 Years 39 Years Transmission and distribution facilities 8,516 7,963 9 to 156 Years 83 Years Services, meters and fire hydrants 3,250 3,062 8 to 93 Years 35 Years General structures and equipment 1,227 1,096 1 to 154 Years 39 Years Waste treatment, pumping and disposal 313 281 2 to 115 Years 46 Years Waste collection 473 399 5 to 109 Years 56 Years Construction work in progress 404 303 Total utility plant 18,099 16,891 Nonutility property 405 378 3 to 50 years 6 Years Total property, plant and equipment $ 18,504 $ 17,269 Property, plant and equipment depreciation expense amounted to $405 , ,

Allowance for Uncollectible Acc

Allowance for Uncollectible Accounts	12 Months Ended
	Dec. 31, 2015
Financing Receivable Allowance For Credit Loss Additional Information [Abstract]
Allowance for Uncollectible Accounts	Note 5: Allowance for Uncollectible Accounts The following table summarizes the changes in the Company’s allowances for uncollectible accounts for the years ended December 31: 2015 2014 2013 Balance as of January 1 $ (35 ) $ (34 ) $ (27 ) Amounts charged to expense (32 ) (37 ) (27 ) Amounts written off 38 43 24 Recoveries of amounts written off (10 ) (7 ) (4 ) Balance as of December 31 $ (39 ) $ (35 ) $ (34 )

Regulatory Assets and Liabiliti

Regulatory Assets and Liabilities	12 Months Ended
	Dec. 31, 2015
Regulatory Assets And Liabilities Disclosure [Abstract]
Regulatory Assets and Liabilities	Note 6: Regulatory Assets and Liabilities Regulatory Assets The regulatory assets represent costs that are probable of recovery from customers in future rates. The majority of the regulatory assets earn a return. The following table summarizes the composition of regulatory assets as of December 31: 2015 2014 Deferred pension expense $ 269 $ 263 Income taxes recoverable through rates 236 229 Removal costs recoverable through rates 225 163 Deferred other postretirement benefit expense 90 107 San Clemente Dam project costs 95 72 Regulatory balancing accounts 88 60 Debt expense 68 71 Purchase premium recoverable through rates 60 60 Deferred tank painting costs 37 37 Other 103 91 Total Regulatory Assets $ 1,271 $ 1,153 The Company’s deferred pension expense includes a portion of the underfunded status that is probable of recovery through rates in future periods of $258 and $248 as of December 31, 2015 and 2014, respectively. The remaining portion is the pension expense in excess of the amount contributed to the pension plans which is deferred by certain subsidiaries and will be recovered in future service rates as contributions are made to the pension plan. The Company has recorded a regulatory asset for the additional revenues expected to be realized when the tax effects of temporary differences previously flowed through to customers reverse. These temporary differences are primarily related to the difference between book and tax depreciation on property placed in service before the adoption by the regulatory authorities of full normalization for rate making purposes. Full normalization requires no flow through of tax benefits to customers. The regulatory asset for income taxes recoverable through rates is net of the reduction expected in future revenues as deferred taxes previously provided, attributable to the difference between the state and federal income tax rates under prior law and the current statutory rates, reverse over the average remaining service lives of the related assets. Removal costs recoverable through rates represent costs incurred for removal of property, plant and equipment or other retirement costs. The Company’s deferred other postretirement benefit expense includes a portion of the underfunded status that is probable of recovery through rates in future periods of $87 and $107 as of December 31, 2015 and 2014, respectively. The remaining portion is postretirement benefit expense in excess of the amount recovered in rates through 1997 has been deferred by certain subsidiaries. These costs are recognized in the rates charged for water service and will be recovered as authorized by the Company’s regulatory authorities. San Clemente Dam project costs represent costs incurred and deferred by the Company’s California subsidiary pursuant to its efforts to investigate alternatives to strengthen or remove the dam due to potential earthquake and flood safety concerns. In June 2012, the California Public Utility Commission (“CPUC”) issued a decision authorizing implementation of a project to reroute the Carmel River and remove the San Clemente Dam. The project includes the Company’s California subsidiary, the California State Conservancy and the National Marine Fisheries Services. Under the order’s terms, the CPUC has authorized recovery of $24 for pre-construction costs, $3 for interim dam safety measures and environmental costs and $49 for construction costs. The authorized costs of $76 are to be recovered via a surcharge over a twenty-year period beginning October 2012. Surcharges collected as of December 31, 2015 and 2014 were $4 and $5, respectively. In addition to the authorized costs, the Company expects to incur additional costs totaling $34, which will be recovered from contributions made by the California State Coastal Conservancy. Contributions collected as of December 31, 2015 and 2014 were $8 and $5, respectively. Regulatory balancing accounts accumulate differences between revenues recognized and authorized revenue requirements until they are collected from customers or are refunded. Regulatory balancing accounts include low income programs and purchased power and water accounts. Debt expense is amortized over the lives of the respective issues. Call premiums on the redemption of long-term debt, as well as unamortized debt expense, are deferred and amortized to the extent they will be recovered through future service rates. Purchase premium recoverable through rates is primarily the recovery of the acquisition premiums related to an asset acquisition by the Company’s California subsidiary during 2002, and acquisitions in 2007 by the Company’s New Jersey subsidiary. As authorized for recovery by the California and New Jersey PUCs, these costs are being amortized to depreciation and amortization in the Consolidated Statements of Operations through November 2048. Tank painting costs are generally deferred and amortized to operations and maintenance expense in the Consolidated Statements of Operations on a straight-line basis over periods ranging from five to fifteen years, as authorized by the regulatory authorities in their determination of rates charged for service. Other regulatory assets include certain deferred business transformation costs, construction costs for treatment facilities, property tax stabilization, employee-related costs, business services project expenses, coastal water project costs, rate case expenditures and environmental remediation costs among others. These costs are deferred because the amounts are being recovered in rates or are probable of recovery through rates in future periods. Regulatory Liabilities The regulatory liabilities generally represent probable future reductions in revenues associated with amounts that are to be credited or refunded to customers through the rate-making process. The following table summarizes the composition of regulatory liabilities as of December 31: 2015 2014 Removal costs recovered through rates $ 311 $ 301 Pension and other postretirement benefit balancing accounts 59 54 Other 32 37 Total Regulatory Liabilities $ 402 $ 392 Removal costs recovered through rates are estimated costs to retire assets at the end of their expected useful life that are recovered through customer rates over the life of the associated assets. In December 2008, the Company’s subsidiary in New Jersey, at the direction of the New Jersey PUC, began to depreciate $48 of the total balance into depreciation and amortization expense in the Consolidated Statements of Operations via straight line amortization through November 2048. Pension and other postretirement benefit balancing accounts represent the difference between costs incurred and costs authorized by the PUC’s that are expected to be refunded to customers. Other regulatory liabilities include legal settlement proceeds, deferred gains and various regulatory balancing accounts.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Note 7: Goodwill and Other Intangible Assets Goodwill The following table summarizes changes in the carrying amount of goodwill for the years ended December 31, 2015 and 2014: Regulated Businesses Market-Based Businesses Consolidated Cost Accumulated Impairment Cost Accumulated Impairment Cost Accumulated Impairment Total Net Balance as of January 1, 2014 $ 3,412 $ (2,332 ) $ 236 $ (108 ) $ 3,648 $ (2,440 ) $ 1,208 Goodwill from acquisitions 3 — 91 — 94 — 94 Balance as of December 31, 2015 $ 3,415 $ (2,332 ) $ 327 $ (108 ) $ 3,742 $ (2,440 ) $ 1,302 The Company recorded goodwill of $91 as part of the Keystone acquisition. The Keystone business is an operating segment comprised of one reporting unit to which all of the goodwill arising from the acquisition was assigned and which is included in the Market-Based Business information. The Company also acquired aggregate goodwill of $3 associated with four of its acquisitions in its Regulated Businesses segment. Excluding goodwill acquired in 2015 related to the Keystone acquisition, the Company determined that no qualitative factors were present that would indicate the estimated fair values of its reporting units were less than the respective carrying values. As such, the Company determined that the two-step goodwill impairment test was not necessary at November 30, 2015 or 2014. A step one test was completed for the Keystone goodwill. We used an income approach valuation technique which estimates the discounted future cash flows of operations. The discounted cash flow analysis relies on a single scenario reflecting best estimate projected cash flows. Significant assumptions were used in estimating the fair value, including the discount rate, growth rate and terminal value. The estimated fair value of the Keystone reporting unit exceeded its carrying value by less than 3% and as such the Company does not believe the goodwill is impaired. If a further decline in the fair value were to occur the Keystone reporting unit could be at risk of failing step one of the goodwill impairment test. There can be no assurances that the Company will not be required to recognize an impairment of goodwill in the future due to market conditions or other factors related to the performance of the Company’s reporting units. These market events could include a decline over a period of time of the Company’s stock price, a decline over a period of time in valuation multiples of comparable water utilities and reporting unit companies, the lack of an increase in the Company’s market price consistent with its peer companies, decreases in control premiums or continued downward pressure on commodity prices. A decline in the forecasted results in our business plan, such as changes in rate case results or capital investment budgets or changes in our interest rates, could also result in an impairment charge. In regards to the Keystone goodwill, adverse developments in market conditions, including prolonged depression of natural gas prices or other factors that negatively impact our forecast operating results, cash flows or key assumptions in the future could result in an impairment charge of a portion or all of the goodwill balance. Other Intangible Assets Included in other long-term assets as of December 31, 2015, is a $12 customer relationship intangible resulting from the Keystone acquisition. This intangible is being amortized on a straight-line basis over a period of eight years.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Stockholders' Equity	Note 8: Stockholders’ Equity Common Stock Under the dividend reinvestment and direct stock purchase plan (the “DRIP”), stockholders may reinvest cash dividends and purchase additional Company common stock, up to certain limits, through the plan administrator without commission fees. Shares purchased by participants through the DRIP may be newly-issued shares, treasury shares, or at the Company’s election, shares purchased by the plan administrator in the open market or in privately negotiated transactions. Purchases generally will be made and credited to DRIP accounts once each week. As of December 31, 2015, there were approximately 4.5 shares available for future issuance under the DRIP. Antidilutive Stock Repurchase Program In February 2015, the Company’s Board of Directors authorized an anti-dilutive common stock repurchase program to mitigate the dilutive effect of shares issued through the Company’s dividend reinvestment, employee stock purchase and executive compensation activities. This program allows the Company to purchase up to 10 shares of its outstanding common stock over an unrestricted period of time in the open market or through privately negotiated transactions in order to minimize dilution. The shares repurchased are held as treasury shares, at cost, until cancelled or reissued at the discretion of the Company’s management. As of December 31, 2015, the Company purchased 2.3 shares of common stock in the open market at an aggregate cost of $126 under this program. Accumulated Other Comprehensive Loss The following table presents changes in accumulated other comprehensive loss by component, net of tax, for the years ended December 31, 2015 and 2014: Defined Benefit Plans Accumulated Employee Benefit Plan Funded Status Amortization of Prior Service Cost Amortization of Actuarial Loss Foreign Currency Translation Loss on Cash Flow Hedge Other Beginning balance as of January 1, 2014 $ (70 ) $ 1 $ 31 $ 3 $ — $ (35 ) Other comprehensive loss (income) (46 ) — — — (1 ) (47 ) Ending balance as of December 31, 2014 $ (116 ) $ 1 $ 31 $ 3 $ (1 ) $ (82 ) Other comprehensive loss (income) (10 ) — 5 (1 ) — (6 ) Ending balance as of December 31, 2015 $ (126 ) $ 1 $ 36 $ 2 $ (1 ) $ (88 ) The Company does not reclassify the amortization of defined benefit pension cost components from accumulated other comprehensive loss directly to net income in its entirety, as a portion of these costs have been capitalized as a regulatory asset. These accumulated other comprehensive loss components are included in the computation of net periodic pension cost. See Note 14—Employee Benefits. The amortization of the loss on cash flow hedge is reclassified to net income during the period incurred and is included in interest, net in the accompanying Consolidated Statements of Operations.

Stock Based Compensation

Stock Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Compensation	Note 9: Stock Based Compensation The Company has granted stock option and restricted stock unit (“RSUs”) awards to non-employee directors, officers and other key employees of the Company pursuant to the terms of its 2007 Omnibus Equity Compensation Plan (the “2007 Plan”). The total aggregate number of shares of common stock that may be issued under the 2007 Plan is 15.5. As of December 31, 2015, 8.4 shares were available for grant under the 2007 Plan. Shares issued under the 2007 Plan may be authorized-but-unissued shares of Company stock or reacquired shares of Company stock, including shares purchased by the Company on the open market. The Company recognizes compensation expense for stock awards over the vesting period of the award. The following table presents stock-based compensation expense recorded in operation and maintenance expense in the accompanying Consolidated Statements of Operations for the years ended December 31: 2015 2014 2013 Stock options $ 2 $ 2 $ 3 RSUs 8 10 9 ESPP 1 1 1 Stock-based compensation 11 13 13 Income tax benefit (4 ) (5 ) (5 ) Stock-based compensation expense, net of tax $ 7 $ 8 $ 8 There were no significant stock-based compensation costs capitalized during the years ended December 31, 2015, 2014 and 2013. The cost of services received from employees in exchange for the issuance of stock options and restricted stock awards is measured based on the grant date fair value of the awards issued. The value of stock options and RSUs awards at the date of the grant is amortized through expense over the three-year service period. All awards granted in 2015, 2014 and 2013 are classified as equity. The Company receives a tax deduction based on the intrinsic value of the award at the exercise date for stock options and the distribution date for RSUs. For each award, throughout the requisite service period, the Company recognizes the tax benefits, which have been included in deferred income tax assets, related to compensation costs. The tax deductions in excess of the benefits recorded throughout the requisite service period are recorded to common stockholders’ equity or the statement of operations and are presented in the financing section of the Consolidated Statements of Cash Flows. The Company stratified its grant populations and used historic employee turnover rates to estimate employee forfeitures. The estimated rate is compared to the actual forfeitures at the end of the reporting period and adjusted as necessary. Stock Options In 2015, 2014 and 2013, the Company granted non-qualified stock options to certain employees under the 2007 Plan. The stock options vest ratably over the three-year service period beginning on January 1 of the year of the grant. These awards have no performance vesting conditions and the grant date fair value is amortized through expense over the requisite service period using the straight-line method and is included in operations and maintenance expense in the accompanying Consolidated Statements of Operations. The following table summarizes the weighted-average assumptions used in the Black-Scholes option-pricing model for grants and the resulting weighted-average grant date fair value per share of stock options granted for the years ended December 31: 2015 2014 2013 Dividend yield 2.35 % 2.55 % 2.52 % Expected volatility 17.64 % 17.75 % 23.50 % Risk-free interest rate 1.48 % 1.06 % 0.70 % Expected life (years) 4.4 3.6 4.3 Exercise price $ 52.75 $ 44.29 $ 39.60 Grant date fair value per share $ 6.21 $ 4.57 $ 5.78 The Company utilized the “simplified method” to determine the expected stock option life due to insufficient historical experience to estimate the exercise patterns of the stock options granted. The Company began granting stock options at the time of its initial public offering in April 2008. Expected volatility is based on a weighted average of historic volatilities of traded common stock of peer companies (regulated water companies) over the expected term of the stock options and historic volatilities of the Company’s common stock during the period it has been publicly traded. The dividend yield is based on the Company’s expected dividend payments and the stock price on the date of grant. The risk-free interest rate is the market yield on U.S. Treasury strips with maturities similar to the expected term of the stock options. The exercise price of the stock options is equal to the fair market value of the underlying stock on the date of option grant. Stock options vest over periods ranging from one to three years and have a maximum term of seven years from the effective date of the grant. As of December 31, 2015, $2 of total unrecognized compensation cost related to nonvested stock options is expected to be recognized over the remaining weighted-average period of 1.6 years. The total grant date fair value of stock options vested was $3 for the years ended December 31, 2015 and 2014 and $4 for the year ended December 31, 2013. The table below summarizes stock option activity for the year ended December 31, 2015: Shares (in thousands) Weighted-Average Exercise Price (per share) Weighted-Average Remaining Life (years) Aggregate Intrinsic Value Options outstanding as January 1, 2015 1,910 $ 33.47 3.9 $ 38 Granted 301 52.75 Forfeited or expired (51 ) 44.36 Exercised (973 ) 31.26 Options outstanding as of December 31, 2015 1,187 $ 39.70 3.9 $ 24 Exercisable as of December 31, 2015 666 $ 32.92 2.6 $ 18 The following table summarizes additional information regarding stock options exercised during the years ended December 31: 2015 2014 2013 Intrinsic value $ 22 $ 13 $ 15 Exercise proceeds 30 15 20 Income tax benefit 7 4 4 RSUs During 2012, the Company granted selected employees an aggregate of 139 thousand RSUs with internal performance measures and, separately, certain market thresholds. These awards vested in January 2015. The terms of the grants specified that to the extent certain performance goals, comprised of internal measures and, separately, market thresholds were achieved, the RSUs would vest; if performance goals were surpassed, up to 175% of the target awards would be distributed; and if performance goals were not met, the awards would be forfeited. In January 2015, an additional 93 thousand RSUs were granted and distributed because performance thresholds were exceeded. In 2015, 2014 and 2013, the Company granted RSUs, both with and without performance conditions, to certain employees under the 2007 Plan. The RSUs without performance conditions vest ratably over the three-year service period beginning January 1 of the year of the grant and the RSUs with performance conditions vest ratably over the three-year performance period beginning January 1 of the year of the grant (the “Performance Period”). Distribution of the performance shares is contingent upon the achievement of internal performance measures and, separately, certain market thresholds over the Performance Period. During 2015, 2014 and 2013, the Company granted RSUs to non-employee directors under the 2007 Plan. The RSUs vested on the date of grant; however, distribution of the shares will be made within 30 days of the earlier of: (i) 15 months after grant date, subject to any deferral election by the director; or (ii) the participant’s separation from service. Because these RSUs vested on the grant date, the total grant date fair value was recorded in operation and maintenance expense included in the expense table above on the grant date. RSUs generally vest over periods ranging from one to three years. RSUs granted with service-only conditions and those with internal performance measures are valued at the market value of the closing price of the Company’s common stock on the date of grant. RSUs granted with market conditions are valued using a Monte Carlo model. Expected volatility is based on historical volatilities of traded common stock of the Company and comparative companies using daily stock prices over the past three years. The expected term is three years and the risk-free interest rate is based on the three-year U.S. Treasury rate in effect as of the measurement date. The following table presents the weighted-average assumptions used in the Monte Carlo simulation and the weighted-average grant date fair values of RSUs granted for the years ended December 31: 2015 2014 2013 Expected volatility 14.93 % 17.78 % 19.37 % Risk-free interest rate 1.07 % 0.75 % 0.40 % Expected life (years) 3.0 3.0 3.0 Grant date fair value per share $ 62.10 $ 45.45 $ 40.13 The grant date fair value of restricted stock awards that vest ratably and have market and/or performance and service conditions are amortized through expense over the requisite service period using the graded-vesting method. RSUs that have no performance conditions are amortized through expense over the requisite service period using the straight-line method and are included in operations expense in the accompanying Consolidated Statements of Operations. As of December 31, 2015, $4 of total unrecognized compensation cost related to the nonvested restricted stock units is expected to be recognized over the weighted-average remaining life of 1.4 years. The total grant date fair value of RSUs vested was $12, $11 and $9 for the years ended December 31, 2015, 2014 and 2013. The table below summarizes restricted stock unit activity for the year ended December 31, 2015: Shares (in thousands) Weighted-Average Grant Date Fair Value (per share) Non-vested total as of January 1, 2015 516 $ 41.46 Granted 156 55.67 Performance share adjustment 93 38.11 Vested (304 ) 39.46 Forfeited (25 ) 45.84 Non-vested total as of December 31, 2015 436 $ 46.97 The following table summarizes additional information regarding RSUs distributed during the years ended December 31: 2015 2014 2013 Intrinsic value $ 17 $ 16 $ 14 Income tax benefit 2 2 2 If dividends are paid with respect to shares of the Company’s common stock before the RSUs are distributed, the Company credits a liability for the value of the dividends that would have been paid if the RSUs were shares of Company common stock. When the RSUs are distributed, the Company pays the participant a lump sum cash payment equal to the value of the dividend equivalents accrued. The Company accrued dividend equivalents totaling $1 to accumulated deficit in the accompanying Consolidated Statements of Changes in Stockholders’ Equity for the years ended December 31, 2015, 2014 and 2013, respectively. Employee Stock Purchase Plan Under the Nonqualified Employee Stock Purchase Plan (“ESPP”), employees can use payroll deductions to acquire Company stock at the lesser of 90% of the fair market value of common stock at either the beginning or the end of a three-month purchase period. As of December 31, 2015, there were 1.2 shares of common stock reserved for issuance under the ESPP. The Company’s ESPP is considered compensatory. During the years ended December 31, 2015, 2014 and 2013, the Company issued 98, 102 and 111 thousand shares, respectively, under the ESPP.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Long-Term Debt	Note 10: Long-Term Debt The Company obtains long-term debt primarily to fund capital expenditures of the regulated subsidiaries and refinance debt of the parent company. The following table summarizes the components of long-term as of December 31: Rate Weighted Average Rate Maturity 2015 2014 Long-term debt of American Water Capital Corp. (a) Senior notes — 3.40%-8.27% 5.23% 2016-2045 $ 4,273 $ 3,753 Private activity bonds and government funded debt — 1.79%-6.25% 5.41% 2021-2040 195 231 Long-term debt of other American Water subsidiaries Private activity bonds and government funded debt — (b) 0.00%-6.20% 4.70% 2016-2041 790 795 Mortgage bonds — fixed rate 4.29%-9.71% 7.41% 2017-2039 637 677 Mandatorily redeemable preferred stock 8.47%-9.75% 8.61% 2019-2036 13 17 Capital lease obligations 12.23% 12.23% 2026 1 1 Long-term debt 5,909 5,474 Unamortized debt premium, net (c) 23 31 Unamortized debt issuance costs (7 ) (6 ) Interest rate swap fair value adjustment 3 4 Total long-term debt $ 5,928 $ 5,503 (a) This indebtedness is considered “debt” for purposes of a support agreement between American Water and American Water Capital Corp. (“AWCC”), which serves as a functional equivalent of a guarantee by AWCC’s payment obligations under such indebtedness. (b) Includes $8 and $10 of variable rate debt with variable-to-fixed interest rate swaps ranging between 4.65% and 3.93%, as of December 31, 2015 and 2014, respectively. This debt was assumed via an acquisition in 2013. (c) Primarily fair value adjustments previously recognized in acquisition purchase accounting. All mortgage bonds and $716 of the private activity bonds and government funded debt held by the subsidiaries were collateralized by utility plant as of December 31, 2015. Long-term debt indentures contain a number of covenants that, among other things, limit, subject to certain exceptions, the Company from issuing debt secured by the Company’s assets. Certain long term notes require the Company to maintain a ratio of consolidated total indebtedness to consolidated total capitalization of not more than 0.70 to 1.00. The ratio as of December 31, 2015 was 0.56 to 1.00. In addition, the Company has $985 of notes which include the right to redeem the notes at par in whole or in part from time to time subject to certain restrictions. The future sinking fund payments and maturities were as follows: Year Amount 2016 $ 54 2017 573 2018 457 2019 166 2020 22 Thereafter 4,637 The following long-term debt was issued in 2015: Company Type Rate Maturity Amount AWCC Senior notes—fixed rate 3.40%-4.30% 2025-2045 $ 550 Other American Water subsidiaries Private activity bonds and government funded debt — 1.00%-1.56% 2032 15 Total issuances $ 565 The Company also assumed debt of $1 as a result of an acquisition during 2015, which has a fixed interest rate of 1.00% and matures in 2040. The Company incurred debt issuance costs of $5 related to the above issuances. The following long-term debt was retired through optional redemption or payment at maturity during 2015: Company Type Rate Maturity Amount AWCC Private activity bonds and government funded debt—fixed rate 1.79%-5.25% 2015-2031 $ 36 AWCC Senior notes — 6.00% 2015 30 Other American Water subsidiaries (a) Private activity bonds and government funded debt — 0.00%-5.40% 2015-2041 61 Other American Water subsidiaries Mandatorily redeemable preferred stock 8.49%-9.18% 2031-2036 4 Total retirements and redemptions $ 131 (a) Includes $2 of non-cash defeasance via the use of restricted funds. Interest, net includes interest income of approximately $13, $11 and $12 in 2015, 2014 and 2013, respectively. One of the principal market risks to which the Company is exposed is changes in interest rates. In order to manage the exposure, the Company follows risk management policies and procedures, including the use of derivative contracts such as swaps. The Company reduces exposure to interest rates by managing commercial paper and debt maturities. The Company does not enter into derivative contracts for speculative purposes and does not use leveraged instruments. The derivative contracts entered into are for periods consistent with the related underlying exposures. The Company is exposed to the risk that counterparties to derivative contracts will fail to meet their contractual obligations. The Company minimizes the counterparty credit risk on these transactions by dealing only with leading, credit-worthy financial institutions having long-term credit ratings of “A” or better. The Company has an interest-rate swap to hedge $100 of its 6.085% fixed-rate debt maturing 2017. The Company pays variable interest of six-month LIBOR plus 3.422%. The swap is accounted for as a fair-value hedge and matures with the fixed-rate debt in 2017. The following table provides a summary of the derivative and fixed rate debt fair value balances recorded by the Company as of December 31, 2015 and 2014, and the line items in the Consolidated Balance Sheets in which such amounts are recorded: Balance Sheet Classification 2015 2014 Regulatory and other long-term assets Other $ 2 $ 4 Long-term debt Long-term debt 2 4 For derivative instruments that are designated and qualify as fair-value hedges, the gain or loss on the hedge instrument as well as the offsetting gain or loss on the hedged item attributable to the hedged risk are recognized in current net income. The Company includes the gain or loss on the derivative instrument and the offsetting gain or loss on the hedged item in interest expense for the years ended December 31 were as follows: Income Statement Classification 2015 2014 2013 Interest, net Loss on swap $ (1 ) $ (1 ) $ (3 ) Gain on borrowing 1 1 3

Short-Term Debt

Short-Term Debt	12 Months Ended
	Dec. 31, 2015
Short Term Borrowings [Abstract]
Short-Term Debt	Note 11: Short-Term Debt Short-term debt consists of commercial paper and credit facility borrowings totaling $628 and $450 as of December 31, 2015 and 2014, respectively. As of December 31, 2015 there were no borrowings outstanding with maturities greater than three months. AWCC has a revolving credit facility with $1,250 in aggregate total commitments from a diversified group of financial institutions. The agreement includes a $150 sublimit for letters of credit and a $100 sublimit for swing loans. On June 30, 2015, AWCC and its lenders extended the termination date of revolving credit facility from October 2018 to June 2020. The amended and restated agreement also allows AWCC to request to further extend the term of the credit facility for up to two one-year periods. Interest on borrowings are based on a LIBOR-based rate, plus an applicable margin. The Company incurred $2 of issuance costs in connection with the extended terms of the credit facility, which will be amortized over the remaining extended life and is included in interest, net in the accompanying Consolidated Statements of Operations. Also, the Company acquired an additional revolving credit facility as part of its Keystone acquisition. The total commitment under this credit facility was $16, of which $14 was available as of December 31, 2015.Interest accrues each day at a rate per annum equal to 2.75% above the greater of the one month or one day LIBOR. The following table summarizes the Company’s aggregate credit facility commitments, letter of credit sub-limit under our revolving credit facility and commercial paper limit, as well as the available capacity for each as of: Available Available Available Credit Facility Credit Facility Letter of Credit Letter of Credit Commercial Paper Commercial Paper Commitment Capacity Sublimit (a) Capacity Limit Capacity December 31, 2015 $ 1,266 $ 1,182 $ 150 $ 68 $ 1,000 $ 374 December 31, 2014 1,250 1,212 150 112 1,000 550 (a) Letters of credit are non-debt instruments maintained to provide credit support for certain transactions as requested by third parties. The Company had $82 and $38 of outstanding letters of credit as of December 31, 2015 and 2014, respectively, all of which were issued under the revolving credit facility noted above. The following table summarizes the short-term borrowing activity for AWCC for the years ended December 31: 2015 2014 Average borrowings $ 553 $ 549 Maximum borrowings outstanding 871 745 Weighted average interest rates, computed on daily basis 0.49 % 0.31 % Weighted average interest rates, as of December 31 0.66 % 0.42 % The credit facility requires the Company to maintain a ratio of consolidated debt to consolidated capitalization of not more than 0.70 to 1.00. The ratio as of December 31, 2015 was 0.56 to 1.00. None of the Company’s borrowings are subject to default or prepayment as a result of a downgrading of securities, although such a downgrading could increase fees and interest charges under the Company’s credit facility. As part of the normal course of business, the Company routinely enters contracts for the purchase and sale of water, energy, fuels and other services. These contracts either contain express provisions or otherwise permit the Company and its counterparties to demand adequate assurance of future performance when there are reasonable grounds for doing so. In accordance with the contracts and applicable contract law, if the Company is downgraded by a credit rating agency, especially if such downgrade is to a level below investment grade, it is possible that a counterparty would attempt to rely on such a downgrade as a basis for making a demand for adequate assurance of future performance. Depending on the Company’s net position with the counterparty, the demand could be for the posting of collateral. In the absence of expressly agreed provisions that specify the collateral that must be provided, the obligation to supply the collateral requested will be a function of the facts and circumstances of the Company’s situation at the time of the demand. If the Company can reasonably claim that it is willing and financially able to perform its obligations, it may be possible that no collateral would need to be posted or that only an amount equal to two or three months of future payments should be sufficient. The Company does not expect to post any collateral which will have a material adverse impact on the Company’s results of operations, financial position or cash flows.

General Taxes

General Taxes	12 Months Ended
	Dec. 31, 2015
General Taxes
General Taxes	Note 12: General Taxes The following table summarizes the components of general tax expense from continuing operations for the years ended December 31: 2015 2014 2013 Gross receipts and franchise $ 99 $ 96 $ 96 Property and capital stock 98 96 94 Payroll 31 31 31 Other general 15 13 13 Total general taxes $ 243 $ 236 $ 234

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Note 13: Income Taxes The following table summarizes the components of income tax expense from continuing operations for the years ended December 31: 2015 2014 2013 Current income taxes State $ 10 $ 11 $ 7 Federal — 15 (20 ) Total current income taxes $ 10 $ 26 $ (13 ) Deferred income taxes State $ 32 $ 31 $ 27 Federal 265 224 225 Amortization of deferred investment tax credits (1 ) (1 ) (2 ) Total deferred income taxes 296 254 250 Provision for income taxes $ 306 $ 280 $ 237 The following is a reconciliation between the statutory federal income tax rate and the Company’s effective tax rate for the years ended December 31: 2015 2014 2013 Income tax at statutory rate 35.0 % 35.0 % 35.0 % Increases (decreases) resulting from: State taxes, net of federal taxes 3.6 3.8 3.6 Flow through differences 0.5 0.4 0.5 Amortization of deferred investment tax credits (0.1 ) (0.1 ) (0.3 ) Subsidiary preferred dividends — 0.1 0.2 Other, net 0.1 0.2 — Provision for income taxes 39.1 % 39.4 % 39.0 % The following table provides the components of the net deferred tax liability from continuing operations as of December 31: 2015 2014 Deferred tax assets Advances and contributions $ 513 $ 502 Other postretirement benefits 76 105 Tax losses and credits 173 197 Pension benefits 105 125 Unamortized debt discount, net 20 20 Other 12 42 Total deferred tax assets 899 991 Valuation allowance (8 ) (10 ) Total deferred tax assets, net of allowance $ 891 $ 981 Deferred tax liabilities Property, plant and equipment, principally due to depreciation differences $ 2,913 $ 2,677 Income taxes recoverable through rates 76 76 Deferred other postretirement benefits 35 65 Deferred pension benefits 104 121 Other 73 76 Total deferred tax liabilities 3,201 3,015 Total deferred tax liabilities, net of deferred tax assets $ (2,310 ) $ (2,034 ) As of December 31, 2015 and 2014, the Company recognized federal net operating loss (“NOL”) carryforwards of $1,080 and $1,005, respectively. The 2015 NOL carryforward includes $37 of windfall tax benefits on stock-based compensation that will not be recorded to equity until the benefit is realized. The Company believes the federal NOL carryforwards are more likely than not to be recovered and require no valuation allowance. The Company’s federal NOL carryforwards will begin to expire in 2028. As of December 31, 2015 and 2014, the Company had state NOLs of $534 and $543, respectively, a portion of which are offset by a valuation allowance because the Company does not believe these NOLs are more likely than not to be realized. The state NOL carryforwards will begin to expire in 2016 through 2034. As of December 31, 2015 and 2014, the Company had Canadian NOL carryforwards of $2 and $6, respectively. The majority of these carryforwards are offset by a valuation allowance because the Company does not believe these NOLs are more likely than not to be realized. The Canadian NOL carryforwards will expire between 2026 through 2034. The Company had capital loss carryforwards for federal income tax purposes of $4 as of December 31, 2015 and 2014. The Company has recognized a full valuation allowance for the capital loss carryforwards because the Company does not believe these losses are more likely than not to be recovered. The Company files income tax returns in the United States federal jurisdiction and various state and foreign jurisdictions. With few exceptions, the Company is no longer subject to U.S. federal, state or local or non-U.S. income tax examinations by tax authorities for years before 2010. For U.S. federal, tax year 2011 is also closed. The Company has state income tax examinations in progress and does not expect material adjustments to result. The Patient Protection and Affordable Care Act (the “PPACA”) became law on March 23, 2010, and the Health Care and Education Reconciliation Act of 2010 became law on March 30, 2010, which makes various amendments to certain aspects of the PPACA (together, the “Acts”). The PPACA effectively changes the tax treatment of federal subsidies paid to sponsors of retiree health benefit plans that provide a benefit that is at least actuarially equivalent to the benefits under Medicare Part D. The Acts effectively make the subsidy payments taxable in tax years beginning after December 31, 2012 and as a result, the Company followed its original accounting for the underfunded status of the other postretirement benefits for the Medicare Part D adjustment and recorded a reduction in deferred tax assets and an increase in its regulatory assets amounting to $6 as of December 31, 2015 and 2014. In connection with the filing of our consolidated 2014 tax return in September 2015, we deducted bonus depreciation, of which approximately $89 of deferred tax liabilities is related to the Regulated Businesses segment. The following table summarizes the changes in the Company’s gross liability, excluding interest and penalties, for unrecognized tax benefits: Balance as of January 1, 2014 $ 178 Increases in current period tax positions 54 Decreases in prior period measurement of tax positions (37 ) Balance as of December 31, 2014 $ 195 Increases in current period tax positions 39 Decreases in prior period measurement of tax positions (1 ) Balance as of December 31, 2015 $ 233 The increase in 2015 current period tax positions related primarily to the Company’s change in tax accounting method filed in 2008 for repair and maintenance costs on its utility plant. The Company does not anticipate material changes to its unrecognized tax benefits within the next year. If the Company sustains all of its positions as of December 31, 2015 and 2014, an unrecognized tax benefit of $9, excluding interest and penalties, would impact the Company’s effective tax rate. The Company had an insignificant amount of interest and penalties related to its tax positions as of December 31, 2015 and 2014. The following table summarizes the changes in the Company’s valuation allowance: Balance as of January 1, 2013 $ 19 Decreases in current period tax positions (6 ) Balance as of December 31, 2013 $ 13 Decreases in current period tax positions (3 ) Balance as of December 31, 2014 $ 10 Decreases in current period tax positions (2 ) Balance as of December 31, 2015 $ 8

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2015
Defined Benefit Plans And Other Postretirement Benefit Plans Disclosures [Abstract]
Employee Benefits	Note 14: Employee Benefits Pension and Other Postretirement Benefits The Company maintains noncontributory defined benefit pension plans covering eligible employees of its regulated utility and shared services operations. Benefits under the plans are based on the employee’s years of service and compensation. The pension plans have been closed for all new employees. The pension plans were closed for most employees hired on or after January 1, 2006. Union employees hired on or after January 1, 2001 had their accrued benefit frozen and will be able to receive this benefit as a lump sum upon termination or retirement. Union employees hired on or after January 1, 2001 and non-union employees hired on or after January 1, 2006 are provided with a 5.25% of base pay defined contribution plan. The Company does not participate in a multiemployer plan. The Company’s pension funding practice is to contribute at least the greater of the minimum amount required by the Employee Retirement Income Security Act of 1974 or the normal cost. Further, the Company will consider additional contributions if needed to avoid “at risk” status and benefit restrictions under the Pension Protection Act of 2006. The Company may also consider increased contributions, based on other financial requirements and the plans’ funded position. Pension plan assets are invested in a number of actively managed and commingled funds including equities, fixed income securities, guaranteed interest contracts with insurance companies, real estate funds and real estate investment trusts (“REITs”). Pension expense in excess of the amount contributed to the pension plans is deferred by certain regulated subsidiaries pending future recovery in rates charged for utility services as contributions are made to the plans. See Note 6—Regulatory Assets and Liabilities. The Company also has unfunded noncontributory supplemental non-qualified pension plans that provide additional retirement benefits to certain employees. The Company maintains other postretirement benefit plans providing varying levels of medical and life insurance to eligible retirees. The retiree welfare plans are closed for union employees hired on or after January 1, 2006. The plans had previously closed for non-union employees hired on or after January 1, 2002. The Company’s policy is to fund other postretirement benefit costs up to the amount recoverable through rates. Assets of the plans are invested in a number of actively managed and commingled funds including equities and fixed income securities. The obligations of the pension and postretirement benefit plans are dominated by obligations for active employees. Because the timing of expected benefit payments is so far in the future, the investment strategy is to allocate a significant percentage of assets to equities, which the Company believes will provide the highest return over the long-term period. The fixed income assets are invested in intermediate and long duration debt securities and may be invested in fixed income instruments, such as futures and options, in order to better match the duration of the plan liability. The Company periodically conducts asset liability studies to ensure the investment strategies are aligned with the profile of the plans’ obligations. None of the Company’s securities are included in pension or other postretirement benefit plan assets. The Company uses fair value for all classes of assets in the calculation of market-related value of plan assets. The investment policy guidelines of the pension plan require that the fixed income portfolio has an overall weighted-average credit rating of A or better by Standard & Poor’s. The investment policies’ objectives are focused on reducing the volatility of the plans’ funding status over a long term horizon. The fair values and asset allocations of pension plan assets as of December 31, 2015 and 2014, respectively, by asset category were as follows: Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Inputs Inputs as of Asset Category 2016 Total (Level 1) (Level 2) (Level 3) December 31, 2015 Cash — $ 5 $ 5 $ — $ — — Equity Securities: U.S. large cap 24 % 318 318 — — 23 % U.S. small cap 8 % 115 115 — — 8 % International 20 % 260 — 260 — 19 % Fixed Income Securities: 40 % 41 % U.S. Treasury and government bonds — 120 95 25 — — Corporate bonds — 375 — 375 — — Mortgage-backed securities — 9 — 9 — — Long duration bond fund — 7 7 — — — Guarantee annuity contracts — 49 — 8 41 — Real Estate 6 % 95 — — 95 7 % REITs 2 % 23 — 23 — 2 % Total 100 % $ 1,376 $ 540 $ 700 $ 136 100 % Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Inputs Inputs as of Asset Category 2015 Total (Level 1) (Level 2) (Level 3) December 31, 2014 Cash — $ 8 $ 8 $ — $ — — Equity Securities: U.S. large cap 24 % 342 342 — — 24 % U.S. small cap 8 % 117 117 — — 8 % International 20 % 274 — 274 — 19 % Fixed Income Securities: 40 % 41 % U.S. Treasury and government bonds — 140 121 19 — — Corporate bonds — 377 — 377 — — Mortgage-backed securities — 4 — 4 — — Long duration bond fund — 7 7 — — — Guarantee annuity contracts — 51 — 9 42 — Real Estate 6 % 85 — — 85 6 % REITs 2 % 23 — 23 — 2 % Total 100 % $ 1,428 $ 595 $ 706 $ 127 100 % The following tables present a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3) for 2015 and 2014, respectively: Level 3 Balance as of January 1, 2015 $ 127 Actual return on assets 12 Purchases, issuances and settlements, net (3 ) Balance as of December 31, 2015 $ 136 Level 3 Balance as of January 1, 2014 $ 44 Actual return on assets 7 Purchases, issuances and settlements, net 76 Balance as of December 31, 2014 $ 127 The Company’s other postretirement benefit plans are partially funded and the assets are held under various trusts. The investments and risk mitigation strategies for the plans are tailored specifically for each trust. In setting new strategic asset mixes, consideration is given to the likelihood that the selected asset allocation will effectively fund the projected plan liabilities and the risk tolerance of the Company. The Company periodically updates the long-term, strategic asset allocations and uses various analytics to determine the optimal asset allocation. Considerations include plan liability characteristics, liquidity characteristics, funding requirements, expected rates of return and the distribution of returns. In June 2012, the Company implemented a de-risking strategy for the medical bargaining trust within the plan to minimize volatility. As part of the de-risking strategy, the Company revised the asset allocations to increase the matching characteristics of assets relative to liabilities. The initial de-risking asset allocation for the plan was 60% return-generating assets and 40% liability-driven assets. The investment strategies and policies for the plan reflect a balance of liability driven and return-generating considerations. The objective of minimizing the volatility of assets relative to liabilities is addressed primarily through asset—liability matching, asset diversification and hedging. The fixed income target asset allocation matches the bond-like and long-dated nature of the postretirement liabilities. Assets are broadly diversified within asset classes to achieve risk-adjusted returns that in total lower asset volatility relative to the liabilities. The Company assesses the investment strategy regularly to ensure actual allocations are in line with target allocations as appropriate. Strategies to address the goal of ensuring sufficient assets to pay benefits include target allocations to a broad array of asset classes and, within asset classes strategies are employed to provide adequate returns, diversification and liquidity. The assets of the Company’s other trusts, within the other postretirement benefit plans, have been primarily invested in equities and fixed income funds. The assets under the various other postretirement benefit trusts are invested differently based on the assets and liabilities of each trust. The obligations of the other postretirement benefit plans are dominated by obligations for the medical bargaining trust. Thirty-nine percent and four percent of the total postretirement plan benefit obligations are related to the medical non-bargaining and life insurance trusts, respectively. Because expected benefit payments related to the benefit obligations are so far into the future, and the size of the medical non-bargaining and life insurance trusts’ obligations are large compared to each trusts’ assets, the investment strategy is to allocate a significant portion of the assets’ investment to equities, which the Company believes will provide the highest long-term return and improve the funding ratio. The Company engages third party investment managers for all invested assets. Managers are not permitted to invest outside of the asset class (e.g. fixed income, equity, alternatives) or strategy for which they have been appointed. Investment management agreements and recurring performance and attribution analysis are used as tools to ensure investment managers invest solely within the investment strategy they have been provided. Futures and options may be used to adjust portfolio duration to align with a plan’s targeted investment policy. In order to minimize asset volatility relative to the liabilities, a portion of plan assets is allocated to fixed income investments that are exposed to interest rate risk. Increases in interest rates generally will result in a decline in the value of fixed income assets while reducing the present value of the liabilities. Conversely, rate decreases will increase fixed income assets, partially offsetting the related increase in the liabilities. Within equities, risk is mitigated by constructing a portfolio that is broadly diversified by geography, market capitalization, manager mandate size, investment style and process. Actual allocations to each asset class vary from target allocations due to periodic investment strategy updates, market value fluctuations, the length of time it takes to fully implement investment allocation, and the timing of benefit payments and contributions. The asset allocation is rebalanced on a quarterly basis, if necessary. The fair values and asset allocations of postretirement benefit plan assets as of December 31, 2015 and 2014, respectively, by asset category, were as follows: Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Inputs Inputs as of Asset Category 2016 Total (Level 1) (Level 2) (Level 3) December 31, 2015 Bargain VEBA: Equity Securities: U.S. large cap 9 % $ 32 $ 32 $ — $ — 9 % International 11 % 38 38 — — 10 % Fixed Income Securities: 80 % 81 % U.S. Treasury and government bonds — 118 118 — — — Corporate bonds — 184 — 184 — — Long duration bond fund — 3 3 — — — Future and option contracts (a) — 1 1 — — — Total Bargain VEBA 100 % $ 376 $ 192 $ 184 $ — 100 % Non-bargain VEBA: Cash — $ 2 $ 2 $ — $ — — Equity Securities: U.S. large cap 21 % 24 24 — — 21 % U.S. small cap 21 % 26 26 — — 22 % International 28 % 33 33 — — 28 % Fixed Income Securities: 30 % 29 % Core fixed income bond fund — 33 33 — — — Total Non-bargain VEBA 100 % $ 118 $ 118 $ — $ — 100 % Life VEBA: Equity Securities: U.S. large cap 70 % $ 4 $ 4 $ — $ — 68 % Fixed Income Securities: 30 % 32 % Core fixed income bond fund — 2 2 — — — Total Life VEBA 100 % $ 6 $ 6 $ — $ — 100 % Total 100 % $ 500 $ 316 $ 184 $ — 100 % (a) Includes cash for margin requirements. Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Assets Inputs Inputs as of Asset Category 2015 Total (Level 1) (Level 2) (Level 3) December 31, 2014 Bargain VEBA: Equity Securities: U.S. large cap 9 % $ 34 $ 34 $ — $ — 9 % International 11 % 41 41 — — 10 % Fixed Income Securities: 80 % 81 % U.S. Treasury and government bonds — 155 155 — — — Corporate bonds — 168 — 168 — — Long duration bond fund — 3 3 — — — Future and option contracts (a) — 1 1 — — — Total Bargain VEBA 100 % $ 402 $ 234 $ 168 $ — 100 % Non-bargain VEBA: Cash — $ 1 $ 1 $ — $ — — Equity Securities: U.S. large cap 21 % 22 22 — — 21 % U.S. small cap 21 % 21 21 — — 21 % International 28 % 28 28 — — 28 % Fixed Income Securities: 30 % 30 % Core fixed income bond fund — 31 31 — — — Total Non-bargain VEBA 100 % $ 103 $ 103 $ — $ — 100 % Life VEBA: Equity Securities: U.S. large cap 70 % $ 5 $ 5 $ — $ — 67 % Fixed Income Securities: 30 % 33 % Core fixed income bond fund — 2 2 — — — Total Life VEBA 100 % $ 7 $ 7 $ — $ — 100 % Total 100 % $ 512 $ 344 $ 168 $ — 100 % (a) Includes cash for margin requirements. Valuation Techniques Used to Determine Fair Value Cash—Cash and investments with maturities of three months or less when purchased, including certain short-term fixed-income securities, are considered cash and are included in the recurring fair value measurements hierarchy as Level 1. Equity securities—For equity securities, the trustees obtain prices from pricing services, whose prices are obtained from direct feeds from market exchanges, that the Company is able to independently corroborate. Equity securities are valued based on quoted prices in active markets and categorized as Level 1. Certain equities, such as international securities held in the pension plan are invested in commingled funds. These funds are valued to reflect the plan fund’s interest in the fund based on the reported year-end net asset value. Since net asset value is not directly observable or not available on a nationally recognized securities exchange for the commingled funds, they are categorized as Level 2. Fixed-income securities—The majority of U.S. Treasury securities and government bonds have been categorized as Level 1 because they trade in highly-liquid and transparent markets that the Company can corroborate. The fair values of corporate bonds, mortgage backed securities, certain government bonds and a guaranteed annuity contract are based on evaluated prices that reflect observable market information, such as actual trade information of similar securities, and have been categorized as Level 2 because the valuations are calculated using models which utilize actively traded market data that the Company can corroborate. Certain other guaranteed annuity contracts are categorized as Level 3 because the investments are not publicly quoted. The fund administrator values the fund using the net asset value per fund share, derived from the quoted prices in active markets of the underlying securities. Since these valuation inputs are not highly observable, these contracts have been categorized as Level 3. Exchange-traded future and option positions are reported in accordance with changes in daily variation margins that are settled daily. Exchange-traded options and futures, for which market quotations are readily available, are valued at the last reported sale price or official closing price on the primary market or exchange on which they are traded and are classified as Level 1. Real estate fund—Real estate fund is valued using the net asset value based on valuation models of underlying securities which generally include significant unobservable inputs that cannot be corroborated using verifiable observable market data. Real estate fund is categorized as Level 3 as the fund uses significant unobservable inputs for fair value measurement. REITs—REITs are invested in commingled funds. Commingled funds are valued to reflect the plan fund’s interest in the fund based on the reported year-end net asset value. Since the net asset value is not directly observable for the commingled funds, they are categorized as Level 2. The following table provides a rollforward of the changes in the benefit obligation and plan assets for the most recent two years for all plans combined: Pension Benefits Other Benefits 2015 2014 2015 2014 Change in benefit obligation Benefit obligation as of January 1, $ 1,746 $ 1,494 $ 703 $ 562 Service cost 37 32 14 11 Interest cost 74 76 30 29 Plan participants' contributions — — 2 2 Actuarial (gain) loss (76 ) 256 (58 ) 123 Gross benefits paid (61 ) (112 ) (26 ) (26 ) Federal subsidy — — 2 2 Benefit obligation as of December 31, $ 1,720 $ 1,746 $ 667 $ 703 Change in plan assets Fair value of plan assets as of January 1, $ 1,428 $ 1,384 $ 512 $ 475 Actual return on plan assets (21 ) 116 (15 ) 49 Employer contributions 30 40 27 12 Plan participants' contributions — — 2 2 Benefits paid (61 ) (112 ) (26 ) (26 ) Fair value of plan assets as of December 31, $ 1,376 $ 1,428 $ 500 $ 512 Funded status as of December 31, $ (344 ) $ (318 ) $ (167 ) $ (191 ) Amounts recognized in the balance sheet consist of: Noncurrent asset $ — $ — $ 2 $ 1 Current liability (2 ) (2 ) — — Noncurrent liability (342 ) (316 ) (169 ) (192 ) Net amount recognized $ (344 ) $ (318 ) $ (167 ) $ (191 ) Benefits paid in 2014 include $56 from a one-time lump sum window offering to retired vested participants. The following table provides the components of the Company’s accumulated other comprehensive income and regulatory assets that have not been recognized as components of periodic benefit costs as of December 31: Pension Benefits Other Benefits 2015 2014 2015 2014 Net actuarial loss $ 397 $ 379 $ 97 $ 119 Prior service cost (credit) 3 4 (10 ) (12 ) Net amount recognized $ 400 $ 383 $ 87 $ 107 Regulatory assets $ 258 $ 248 $ 87 $ 107 Accumulated other comprehensive income 142 135 — — Total $ 400 $ 383 $ 87 $ 107 As of December 31, 2015 and 2014, the projected benefit obligation, accumulated benefit obligation and fair value of plan assets for pension plans with a projected obligation in excess of plan assets were as follows: Projected Benefit Obligation Exceeds the Fair Value of Plans' Assets 2015 2014 Projected benefit obligation $ 1,721 $ 1,746 Fair value of plan assets 1,376 1,428 Accumulated Benefit Obligation Exceeds the Fair Value of Plans' Assets 2015 2014 Accumulated benefit obligation $ 1,584 $ 1,616 Fair value of plan assets 1,376 1,428 The accumulated postretirement benefit obligation exceeds plan assets for all of the Company’s other postretirement benefit plans. In August 2006, the Pension Protection Act (“PPA”) was signed into law in the U.S. The PPA replaces the funding requirements for defined benefit pension plans by requiring that defined benefit plans contribute to 100% of the current liability funding target over seven years. Defined benefit plans with a funding status of less than 80% of the current liability are defined as being “at risk” and additional funding requirements and benefit restrictions may apply. The PPA was effective for the 2008 plan year with short-term phase-in provisions for both the funding target and at-risk determination. The Company’s qualified defined benefit plan is currently funded above the at-risk threshold, and therefore the Company expects that the plans will not be subject to the “at risk” funding requirements of the PPA. The Company is proactively monitoring the plan’s funded status and projected contributions under the law to appropriately manage the potential impact on cash requirements. Minimum funding requirements for the qualified defined benefit pension plan are determined by government regulations and not by accounting pronouncements. The Company plans to contribute amounts at least equal to the greater of the minimum required contributions or the normal cost in 2016 to the qualified pension plans. The Company plans to contribute to its 2016 other postretirement benefit cost for rate-making purposes. Information about the expected cash flows for the pension and postretirement benefit plans is as follows: Pension Other Benefits Benefits 2016 expected employer contributions To plan trusts $ 33 $ 22 To plan participants 2 — The Company made 2016 contributions to fund pension benefits and other benefits of $9 and $6, respectively, through February 2016. The following table reflects the net benefits expected to be paid from the plan assets or the Company’s assets: Pension Benefits Other Benefits Expected Benefit Payments Expected Benefit Payments Expected Federal Subsidy Payments 2016 $ 65 $ 28 $ 2 2017 70 30 2 2018 76 32 2 2019 82 35 3 2020 89 37 3 2021-2025 525 212 18 Because the above amounts are net benefits, plan participants’ contributions have been excluded from the expected benefits. Accounting for pensions and other postretirement benefits requires an extensive use of assumptions about the discount rate, expected return on plan assets, the rate of future compensation increases received by the Company’s employees, mortality, turnover and medical costs. Each assumption is reviewed annually. The assumptions are selected to represent the average expected experience over time and may differ in any one year from actual experience due to changes in capital markets and the overall economy. These differences will impact the amount of pension and other postretirement benefit expense that the Company recognizes. The significant assumptions related to the Company’s pension and other postretirement benefit plans were as follows: Pension Benefits Other Benefits 2015 2014 2013 2015 2014 2013 Weighted-average assumptions used to determine December 31 benefit obligations Discount rate 4.66% 4.24% 5.12% 4.67% 4.24% 5.10% Rate of compensation increase 3.10% 3.12% 3.15% N/A N/A N/A Medical trend N/A N/A N/A graded from graded from graded from 6.50% in 2015 6.75% in 2014 7.00% in 2013 to 5.00% in 2021+ to 5.00% in 2021+ to 5.00% in 2019+ Weighted-average assumptions used to determine net periodic cost Discount rate 4.24% 5.12% 4.17% 4.24% 5.10% 4.16% Expected return on plan assets 6.91% 6.91% 7.49% 4.92% 5.87% 6.99% Rate of compensation increase 3.12% 3.15% 3.19% N/A N/A N/A Medical trend N/A N/A N/A graded from graded from graded from 6.75% in 2015 7.00% in 2014 7.25% in 2013 to 5.00% in 2021+ to 5.00% in 2019+ to 5.00% in 2019+ N/A—Assumption is not applicable. The discount rate assumption was determined for the pension and postretirement benefit plans independently. At year-end 2011, the Company began using an approach that approximates the process of settlement of obligations tailored to the plans’ expected cash flows by matching the plans’ cash flows to the coupons and expected maturity values of individually selected bonds. The yield curve was developed for a universe containing the majority of U.S.-issued AA-graded corporate bonds, all of which were non callable (or callable with make-whole provisions). Historically, for each plan, the discount rate was developed as the level equivalent rate that would produce the same present value as that using spot rates aligned with the projected benefit payments. The expected long-term rate of return on plan assets is based on historical and projected rates of return, prior to administrative and investment management fees, for current and planned asset classes in the plans’ investment portfolios. Assumed projected rates of return for each of the plans’ projected asset classes were selected after analyzing historical experience and future expectations of the returns and volatility of the various asset classes. Based on the target asset allocation for each asset class, the overall expected rate of return for the portfolio was developed, adjusted for historical and expected experience of active portfolio management results compared to the benchmark returns and for the effect of expenses paid from plan assets. The Company’s pension expense increases as the expected return on assets decreases. The Company used an expected return on plan assets of 7.02% and 5.20% to estimate its 2016 pension and other postretirement benefit costs, respectively. In the determination of year end 2014 projected benefit plan obligations, the Company adopted a new table based on the Society of Actuaries RP 2014 mortality table including a generational BB-2D projection scale. The adoption resulted in a significant increase to pension and other postretirement benefit plans’ projected benefit obligations. In 2015 a new RP 2015 mortality table was issued. All of the experience upon which the table is based was considered by the Company in selecting its 2014 assumptions. Assumed health care cost trend rates have a significant effect on the amounts reported for the other postretirement benefit plans. The health care cost trend rate is based on historical rates and expected market conditions. A one-percentage-point change in assumed health care cost trend rates would have the following effects: One-Percentage-Point Increase One-Percentage-Point Decrease Effect on total of service and interest cost components $ 8 $ (6 ) Effect on other postretirement benefit obligation $ 99 $ (81 ) The following table provides the components of net periodic benefit costs for the years ended December 31: 2015 2014 2013 Components of net periodic pension benefit cost Service cost $ 37 $ 32 $ 37 Interest cost 74 76 68 Expected return on plan assets (97 ) (95 ) (88 ) Amortization of: Prior service cost (credit) 1 1 1 Actuarial (gain) loss 25 — 37 Net periodic pension benefit cost $ 40 $ 14 $ 55 Other changes in plan assets and benefit obligations recognized in other comprehensive income Amortization of prior service credit (cost) $ — $ — $ — Current year actuarial (gain) loss 10 46 (73 ) Amortization of actuarial gain (loss) (5 ) — (9 ) Total recognized in other comprehensive income $ 5 $ 46 $ (82 ) Total recognized in net periodic benefit cost and comprehensive income $ 45 $ 60 $ (27 ) Components of net periodic other postretirement benefit cost Service cost $ 14 $ 11 $ 15 Interest cost 30 29 29 Expected return on plan assets (26 ) (28 ) (30 ) Amortization of: Prior service cost (credit) (2 ) (2 ) (2 ) Actuarial (gain) loss 5 — 11 Net periodic other postretirement benefit cost $ 21 $ 10 $ 23 The Company’s policy is to recognize curtailments when the total expected future service of plan participants is reduced by greater than 10% due to an event that results in terminations and/or retirements. Cumulative gains and losses that are in excess of 10% of the greater of either the projected benefit obligation or the fair value of plan assets are amortized over the expected average remaining future service of the current active membership for the plans. The estimated amounts that will be amortized from accumulated other comprehensive income and regulatory assets into net periodic benefit cost in 2016 are as follows: Pension Benefits Other Benefits Actuarial (gain) loss $ 27 $ 3 Prior service cost (credit) 1 (2 ) Total $ 28 $ 1 Savings Plans for Employees The Company maintains 401(k) savings plans that allow employees to save for retirement on a tax-deferred basis. Employees can make contributions that are invested at their direction in one or more funds. The Company makes matching contributions based on a percentage of an employee’s contribution, subject to certain limitations. Due to the Company’s discontinuing new entrants into the defined benefit pension plan, on January 1, 2006 the Company began providing an additional 5.25% of base pay defined contribution benefit for union employees hired on or after January 1, 2001 and non-union employees hired on or after January 1, 2006. Plan expenses totaled $9, $8 and $8 for 2015, 2014 and 2013, respectively. All of the Company’s contributions are invested in one or more funds at the direction of the employees.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 15: Commitments and Contingencies Commitments Commitments have been made in connection with certain construction programs. The estimated capital expenditures required under legal and binding contractual obligations amounted to $238 as of December 31, 2015. The Company’s regulated subsidiaries maintain agreements with other water purveyors for the purchase of water to supplement their water supply. The future annual commitments related to minimum quantities of purchased water having non-cancelable terms are as follows: Year Amount 2016 $ 51 2017 45 2018 44 2019 43 2020 44 Thereafter 383 The Company enters into agreements for the provision of services to water and wastewater facilities for the United States military, municipalities and other customers. The Company’s military agreements expire between 2051 and 2065 and have remaining performance commitments as measured by estimated remaining contract revenue of $2,784 as of December 31, 2015. The military agreements are subject to customary termination provisions held by the U.S. Federal Government prior to the agreed upon contract expiration. The Company’s O&M agreements with municipalities and other customers expire between 2016 and 2048 and have remaining performance commitments as measured by estimated remaining contract revenue of $795 as of December 31, 2015. Some of the Company’s long-term contracts to operate and maintain a municipality’s, federal government’s or other party’s water or wastewater treatment and delivery facilities include responsibility for certain maintenance for some of those facilities, in exchange for an annual fee. Unless specifically required to perform certain maintenance activities, the maintenance costs are recognized when the maintenance is performed. Contingencies The Company is routinely involved in legal actions incident to the normal conduct of its business. As of December 31, 2015, the Company has accrued approximately $5 of probable loss contingencies and has estimated that the maximum amount of losses associated with reasonably possible loss contingencies that can be reasonably estimated is $36. For certain matters, claims and actions, the Company is unable to estimate possible losses. The Company believes that damages or settlements, if any, recovered by plaintiffs in such matters, claims or actions, other than as described in this Note 15, will not have a material adverse effect on the Company. West Virginia Elk River Freedom Industries Chemical Spill On January 9, 2014, a chemical storage tank owned by Freedom Industries, Inc. leaked two substances, 4-methylcyclohexane methanol, or MCHM, and PPH/DiPPH, a mix of polyglycol ethers, into the Elk River near the West Virginia-American Water Company (“WVAWC”) treatment plant intake in Charleston, West Virginia. After having been alerted to the leak of MCHM by the West Virginia Department of Environmental Protection (“DEP”), WVAWC took immediate steps to gather more information about MCHM, augment its treatment process as a precaution, and begin consultations with federal, state and local public health officials. As soon as possible after it was determined that the augmented treatment process would not fully remove the MCHM, a joint decision was reached in consultation with the West Virginia Bureau for Public Health to issue a “Do Not Use” order for all of its approximately 93,000 customer accounts in parts of nine West Virginia counties served by the Charleston treatment plant. The order addressed the use of water for drinking, cooking, washing and bathing, but did not affect continued use of water for sanitation and fire protection. Over the next several days, WVAWC and an interagency team of state and federal officials engaged in extensive sampling and testing to determine if levels of MCHM were below one part per million (1 ppm), a level that the U.S. Centers for Disease Control and Prevention (“CDC”) and the U.S. Environmental Protection Agency indicated would be protective of public health. Beginning on January 13, 2014, based on the results of the continued testing, the Do Not Use order was lifted in stages to help ensure the water system was not overwhelmed by excessive demand, which could have caused additional water quality and service issues. By January 18, 2014, none of WVAWC’s customers were subject to the Do Not Use order, although CDC guidance suggesting that pregnant women avoid consuming the water until the chemicals were at non-detectable levels remained in place. In addition, based on saved samples taken on or before January 18, 2014, PPH/DiPPH was no longer detected in the water supply as of January 18, 2014. On February 21, 2014, WVAWC announced that all points of testing throughout its water distribution system indicated that levels of MCHM were below 10 parts per billion (10 ppb). The interagency team established 10 ppb as the “non-detect” level of MCHM in the water distribution system based on the measurement capabilities of the multiple laboratories used. WVAWC continued to work with laboratories to test down to below 2 ppb of MCHM and announced on March 3, 2014, that it had cleared the system to below this level. To date, there are 68 pending cases against WVAWC with respect to this matter in the United States District Court for the Southern District of West Virginia or West Virginia Circuit Courts in Kanawha, Boone and Putnam counties. Fifty-three of the state court cases naming WVAWC, and one case naming both WVAWC and American Water Works Service Company, Inc. (“AWWSC,” and together with WVAWC and the Company, the “American Water Defendants”) were removed to the United States District Court for the Southern District of West Virginia. On December 17, 2015, the federal district court entered orders remanding 52 of the previously removed cases back to the West Virginia Circuit Courts for further proceedings (two of the previously removed cases had been dismissed in the interim). Following that order, seven additional cases were filed against WVAWC in West Virginia Circuit Courts in Kanawha and Putnam counties with respect to this matter. On January 28, 2016, all of the state court cases were referred to West Virginia’s Mass Litigation Panel for further proceedings. Four of the cases pending before the federal district court were consolidated for purposes of discovery, and an amended consolidated class action complaint for those cases (the “Federal action”) was filed on December 9, 2014 by several plaintiffs who allegedly suffered economic losses, loss of use of property and tap water or other specified adverse consequences as a result of the Freedom Industries spill, on behalf of a purported class of all persons and businesses supplied with, using, or exposed to water contaminated with Crude MCHM and provided by WVAWC in Logan, Clay, Lincoln, Roane, Jackson, Boone, Putnam, and Kanawha Counties and the Culloden area of Cabell County, West Virginia as of January 9, 2014. The amended consolidated complaint names several individuals and corporate entities as defendants, including the American Water Defendants. The plaintiffs seek unspecified damages for alleged business or economic losses; unspecified damages or a mechanism for recovery to address a variety of alleged costs, loss of use of property, personal injury and other consequences allegedly suffered by purported class members; punitive damages and certain additional relief, including the establishment of a medical monitoring program to protect the purported class members from an alleged increased risk of contracting serious latent disease. On April 9, 2015, the court in the Federal action denied a motion to dismiss all claims against the Company for lack of personal jurisdiction. A separate motion to dismiss filed by AWWSC and WVAWC (and joined by the Company) asserting various legal defenses in the Federal action was resolved by the court on June 3, 2015. The court dismissed three causes of action but denied the motion to dismiss with respect to the remaining causes of actions and allowed the plaintiffs to continue to pursue the various claims for damages alleged in their amended consolidated complaint. On July 6, 2015, the plaintiffs filed a motion seeking certification of a class defined to include persons who resided in dwellings served by WVAWC’s Kanawha Valley Treatment Plant (“KVTP”) on January 9, 2014, persons who owned businesses served by the KVTP on January 9, 2014, and hourly employees who worked for such businesses. The plaintiffs sought a class-wide determination of liability against the American Water Defendants, among others, and of damages to the three groups of plaintiffs as a result of the “Do Not Use” order issued after the Freedom Industries spill. A court-directed mediation was held at the end of September 2015 with the assistance of private mediators. Representatives of the American Water Defendants, Eastman Chemical, the Federal action plaintiffs, and the plaintiffs in the 53 state court cases as to which removal to Federal court had been sought, as well as insurance carriers for certain of the defendants, participated in the mediation. No resolution was reached and no further mediation discussions have been scheduled to date. On October 8, 2015, the court in the Federal action granted in part and denied in part the plaintiffs’ class certification motion. The court certified a class addressing the alleged fault of Eastman Chemical for tort claims and the alleged fault of the American Water Defendants for tort and breach of contract claims, as well as the comparative fault of Freedom Industries. However, the court granted the joint motion by defendants to exclude certain expert testimony, disallowing the testimony of plaintiffs’ economic damages experts, and denied class certification as to any damages, including punitive damages. Thus, determination or quantification of damages, if any, would be made in subsequent proceedings on an individual basis. On December 17, 2015, the court in the Federal action entered a scheduling order that provides for the trial on class issues to begin in July 2016. During the first week of January 2016, three additional cases were filed against one or more of the American Water Defendants, as well as others, in the U.S. District Court for the Southern District of West Virginia with respect to this matter. Additionally, investigations with respect to the matter have been initiated by the Chemical Safety Board, the U.S. Attorney’s Office for the Southern District of West Virginia, the West Virginia Attorney General, and the Public Service Commission of West Virginia (the “PSC”). As a result of the U.S. Attorney’s Office investigation, Freedom Industries and six former Freedom Industries employees (three of whom also were former owners of Freedom Industries), pled guilty to violations of the federal Clean Water Act. On May 21, 2014, the PSC issued an Order initiating a General Investigation into certain matters relating to WVAWC's response to the Freedom Industries spill. Three parties have intervened in the proceeding, including the Consumer Advocate Division of the PSC and two attorney-sponsored groups, including one sponsored by some of the plaintiffs’ counsel involved in the civil litigation described above. WVAWC has filed testimony regarding its response to the spill and is subject to discovery from PSC staff and the intervenors as part of the General Investigation. Several disputes have arisen between the WVAWC and the intervenors regarding, among other things, the scope of the discovery and the maintenance of confidentiality with regard to certain WVAWC emergency planning documents. In addition, the intervenors and PSC staff filed expert testimony in support of their assertions that WVAWC did not act reasonably with respect to the Freedom Industries spill, and WVAWC has asserted that some of the testimony is outside the scope of the PSC proceeding. The PSC has deferred setting a revised procedural schedule and has not set a final hearing date on the matter. The Company believes that the causes of action and other claims asserted against the American Water Defendants in the proceedings described above are without merit and continues to vigorously defend itself in these proceedings. Given the current stage of these proceedings, the Company cannot reasonably estimate the amount of any reasonably possible losses or a range of such losses related to these proceedings.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Common Share	Note 16: Earnings per Common Share The following is a reconciliation of the numerator and denominator for basic and diluted earnings per share (“EPS”) calculations for the years ended December 31: 2015 2014 2013 Numerator Income from continuing operations $ 476 $ 430 $ 371 Loss from discontinued operations, net of tax — (7 ) (2 ) Net income available to common stockholders $ 476 $ 423 $ 369 Denominator Weighted average common shares outstanding — 179 179 178 Effect of dilutive common stock equivalents 1 1 1 Weighted average common shares outstanding—Diluted 180 180 179 The effect of dilutive common stock equivalents is related to the RSUs and stock options granted under the 2007 Plan, and shares purchased under the ESPP. Less than one million share-based awards were excluded from the computation of diluted EPS for the years ended December 31, 2015, 2014 and 2013 because their effect would have been anti-dilutive under the treasury stock method.

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	Note 17: Fair Values of Financial Instruments The following methods and assumptions were used by the Company in estimating its fair value disclosures for financial instruments: Current assets and current liabilities—The carrying amounts reported in the Consolidated Balance Sheets for current assets and current liabilities, including revolving credit debt, due to the short-term maturities and variable interest rates, approximate their fair values. Preferred stock with mandatory redemption requirements and long-term debt—The fair values of preferred stock with mandatory redemption requirements and long-term debt are categorized within the fair value hierarchy based on the inputs that are used to value each instrument. The fair value of long-term debt classified as Level 1 is calculated using quoted prices in active markets. Level 2 instruments are valued using observable inputs and Level 3 instruments are valued using observable and unobservable inputs. The fair values of instruments classified as Level 2 and 3 are determined by a valuation model that is based on a conventional discounted cash flow methodology and utilizes assumptions of current market rates. As a majority of the Company’s debts do not trade in active markets, the Company calculated a base yield curve using a risk-free rate (a U.S. Treasury securities yield curve) plus a credit spread that is based on the following two factors: an average of the Company’s own publicly-traded debt securities and the current market rates for U.S. Utility A debt securities. The Company used these yield curve assumptions to derive a base yield for the Level 2 and Level 3 securities. Additionally, the Company adjusted the base yield for specific features of the debt securities including call features, coupon tax treatment and collateral for the Level 3 instruments. The carrying amounts, including fair value adjustments previously recognized in acquisition purchase accounting and a fair value adjustment related to the Company’s interest rate swap fair value hedge (which is classified as Level 2 in the fair value hierarchy), and fair values of the financial instruments were as follows: Carrying December 31, 2015 Amount L e Level 2 Level 3 Total Preferred stock with mandatory redemption requirements $ 13 $ — $ — $ 18 $ 18 Long-term debt (excluding capital lease obligations) 5,914 3,397 1,419 1,941 6,757 Carrying December 31, 2014 Amount Level 1 Level 2 Level 3 Total Preferred stock with mandatory redemption requirements $ 17 $ — $ — $ 22 $ 22 Long-term debt (excluding capital lease obligations) 5,485 2,874 1,475 2,055 6,404 Fair Value Measurements To increase consistency and comparability in fair value measurements, GAAP establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows: · Level 1—quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access as of the reporting date. Financial assets and liabilities utilizing Level 1 inputs include active exchange-traded equity securities, exchange-based derivatives, mutual funds and money market funds. · Level 2—inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. Financial assets and liabilities utilizing Level 2 inputs include fixed income securities, non-exchange-based derivatives, commingled investment funds not subject to purchase and sale restrictions and fair-value hedges. · Level 3—unobservable inputs, such as internally-developed pricing models for the asset or liability due to little or no market activity for the asset or liability. Financial assets and liabilities utilizing Level 3 inputs include infrequently-traded non-exchange-based derivatives and commingled investment funds subject to purchase and sale restrictions. Recurring Fair Value Measurements The following table presents assets and liabilities measured and recorded at fair value on a recurring basis and their level within the fair value hierarchy as of December 31, 2015 and 2014, respectively: December 31, 2015 Level 1 Level 2 Level 3 Total Assets Restricted funds $ 27 $ — $ — $ 27 Rabbi trust investments 12 12 Deposits 1 — — 1 Mark-to-market derivative asset — 2 — 2 Other investments 4 — — 4 Total assets 44 2 — 46 Liabilities Deferred compensation obligation 11 — — 11 Mark-to-market derivative liability — 1 — 1 Total liabilities 11 1 — 12 Total net assets $ 33 $ 1 $ — $ 34 December 31, 2014 Level 1 Level 2 Level 3 Total Assets Restricted funds $ 23 $ — $ — $ 23 Rabbi trust investments — 12 — 12 Deposits 4 — — 4 Mark-to-market derivative asset — 4 — 4 Other investments 22 — — 22 Total assets 49 16 — 65 Liabilities Deferred compensation obligation — 12 — 12 Mark-to-market derivative liability — 1 — 1 Total liabilities — 13 — 13 Total net assets $ 49 $ 3 $ — $ 52 Restricted funds—The Company’s restricted funds primarily represent proceeds received from financings for the construction and capital improvement of facilities and from customers for future services under operations and maintenance projects. The proceeds of these financings are held in escrow until the designated expenditures are incurred. Long-term restricted funds of $6 and $9 were included in other long-term assets as of December 31, 2015 and 2014, respectively. Rabbi trust investments—The Company’s rabbi trust investments consist of equity and index funds from which supplemental executive retirement plan benefits and deferred compensation obligations can be paid. The Company includes these assets in other long-term assets. Deposits—Deposits include escrow funds and certain other deposits held in trust. The Company includes cash deposits in other current assets. Deferred compensation obligations—The Company’s deferred compensation plans allow participants to defer certain cash compensation into notional investment accounts. The Company includes such plans in other long-term liabilities. The value of the Company’s deferred compensation obligations is based on the market value of the participants’ notional investment accounts. The notional investments are comprised primarily of mutual funds, which are based on observable market prices. Mark-to-market derivative asset and liability—The Company utilizes fixed-to-floating interest-rate swaps, typically designated as fair-value hedges, to achieve a targeted level of variable-rate debt as a percentage of total debt. The Company also employs derivative financial instruments in the form of variable-to-fixed interest rate swaps, classified as economic hedges, in order to fix the interest cost on some of its variable-rate debt. The Company uses a calculation of future cash inflows and estimated future outflows, which are discounted, to determine the current fair value. Additional inputs to the present value calculation include the contract terms, counterparty credit risk, interest rates and market volatility. Other investments—Other investments primarily represent money market funds used for active employee benefits. The Company includes other investments in other current assets.

Leases

Leases	12 Months Ended
	Dec. 31, 2015
Leases [Abstract]
Leases	Note 18: Leases The Company has entered into operating leases involving certain facilities and equipment. Rental expenses under operating leases were $21 for 2015, $22 for 2014 and $23 for 2013. The operating leases for facilities will expire over the next 25 years and the operating leases for equipment will expire over the next five years. Certain operating leases have renewal options ranging from one to five years. The minimum annual future rental commitment under operating leases that have initial or remaining non-cancelable lease terms over the next five years and thereafter are as follows: Year Amount 2016 $ 13 2017 12 2018 11 2019 10 2020 8 Thereafter 74 The Company has a series of agreements with various public entities (the “Partners”) to establish certain joint ventures, commonly referred to as “public-private partnerships.” Under the public-private partnerships, the Company constructed utility plant, financed by the Company and the Partners constructed utility plant (connected to the Company’s property), financed by the Partners. The Company agreed to transfer and convey some of its real and personal property to the Partners in exchange for an equal principal amount of Industrial Development Bonds (“IDBs”), issued by the Partners under a state Industrial Development Bond and Commercial Development Act. The Company leased back the total facilities, including portions funded by both the Company and the Partners, under leases for a period of 40 years. The leases related to the portion of the facilities funded by the Company have required payments from the Company to the Partners that approximate the payments required by the terms of the IDBs from the Partners to the Company (as the holder of the IDBs). As the ownership of the portion of the facilities constructed by the Company will revert back to the Company at the end of the lease, the Company has recorded these as capital leases. The lease obligation and the receivable for the principal amount of the IDBs are presented by the Company on a net basis. The gross cost of the facilities funded by the Company recognized as a capital lease asset was $156 and $157 as of December 31, 2015 and 2014, respectively, which is presented in property, plant and equipment in the accompanying Consolidated Balance Sheets. The future payments under the lease obligations are equal to and offset by the payments receivable under the IDBs. As of December 31, 2015, the minimum annual future rental commitment under the operating leases for the portion of the facilities funded by the Partners that have initial or remaining non-cancelable lease terms in excess of one year included in the preceding minimum annual rental commitments are $4 in 2016 through 2020, and $69 thereafter.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	Note 19: Segment Information The Company’s operating segments are comprised of the revenue-generating components of its businesses for which separate financial information is internally produced and regularly used by management to make operating decisions and assess performance. The Company operates its businesses primarily through one reportable segment, the Regulated Businesses segment. The Company also operates businesses that provide a broad range of related and complementary water and wastewater services in non-regulated markets, which includes four operating segments that individually do not meet the criteria of a reportable segment. These four non-reportable operating segments have been combined and are presented as Market-Based Businesses. The Regulated Businesses segment is the largest component of the Company’s business and includes 18 subsidiaries that provide water and wastewater services to customers in 16 states. The Market-Based Businesses’ four non-reportable operating segments are Military Services Group, Contract Operations Group, Homeowner Services Group and Keystone Operations. Military Services Group performs 50 - The accounting policies of the segments are the same as those described in the summary of significant accounting policies. See Note 2—Significant Accounting Policies. The Regulated Businesses segment and Market-Based Businesses include intercompany costs that are allocated by American Water Works Service Company, Inc. and intercompany interest that is charged by American Water Capital Corp., which are eliminated to reconcile to the consolidated results of operations. Inter-segment revenues, which are primarily recorded at cost plus a mark-up that approximates current market prices, includes leased office space, furniture and equipment provided by the Company’s market-based subsidiaries to its regulated subsidiaries. “Other” includes corporate costs that are not allocated to the Company’s operating segments, eliminations of inter-segment transactions, fair value adjustments and associated income and deductions related to the acquisitions that have not been allocated to the operating segments for evaluation of performance and allocation of resource purposes. The adjustments related to the acquisitions are reported in Other as they are excluded from segment performance measures evaluated by management. The chief operating decision maker of the company, who is the President and Chief Executive Officer, uses income from continuing operations before income tax as the primary measure of profit and loss in assessing the results of each operating segment. The following tables include the Company’s summarized segment information as of and for the years ended December 31: 2015 Regulated Businesses Market-Based Businesses Other Consolidated Operating revenues $ 2,743 $ 434 $ (18 ) $ 3,159 Depreciation and amortization 411 8 21 440 Total operating expenses, net 1,732 370 (18 ) 2,084 Interest, net 248 (2 ) 62 308 Income from continuing operations before income taxes 776 68 (62 ) 782 Provision for income taxes 303 26 (23 ) 306 Income from continuing operations 473 42 (39 ) 476 Total assets 15,258 496 1,487 17,241 Capital expenditures 1,143 17 — 1,160 2014 Regulated Businesses Market-Based Businesses Other Consolidated Operating revenues $ 2,674 $ 355 $ (18 ) $ 3,011 Depreciation and amortization 394 6 24 424 Total operating expenses, net 1,726 300 (18 ) 2,008 Interest, net 248 (2 ) 53 299 Income from continuing operations before income taxes 707 58 (55 ) 710 Provision for income taxes 273 18 (11 ) 280 Income from continuing operations 434 40 (44 ) 430 Total assets (b) 14,343 314 1,381 16,038 Capital expenditures 946 10 — 956 2013 Regulated Businesses Market-Based Businesses Other Consolidated Operating revenues (a) $ 2,594 $ 303 $ (18 ) $ 2,879 Depreciation and amortization (a) 376 6 25 407 Total operating expenses, net (a) 1,700 252 (21 ) 1,931 Interest, net 249 (2 ) 61 308 Income from continuing operations before income taxes (a) 655 53 (100 ) 608 Provision for income taxes 255 14 (32 ) 237 Income from continuing operations 400 39 (68 ) 371 Total assets (b) 13,448 286 1,330 15,064 Assets of discontinued operations (included in total assets above) — 8 — 8 Capital expenditures 973 7 — 980 Capital expenditures of discontinued operations (included in capital expenditures above) — 1 — 1 (a) The information has been revised to reflect the impact of discontinued operations, as applicable. See Note 3—Acquisitions and Divestitures for additional details on the Company’s discontinued operations. (b) The information has been revised to reflect the retrospective application of ASU 2015-15 Presentation of Debt Issuance Costs and ASU 2015-17 Income Taxes. See Note 2–Significant Accounting Policies for additional details.

Unaudited Quarterly Data

Unaudited Quarterly Data	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Unaudited Quarterly Data	Note 20: Unaudited Quarterly Data The following table summarizes certain supplemental unaudited consolidated quarterly financial data for each of the four quarters in the years ended December 31, 2015 and 2014, respectively. The operating results for any quarter are not indicative of results that may be expected for a full year or any future periods. 2015 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Operating revenues $ 698 $ 782 $ 896 $ 783 Operating income 204 278 361 232 Net income attributable to common stockholders 80 123 174 99 Basic earnings per share: Net income attributable to common stockholders 0.45 0.69 0.97 0.55 Diluted earnings per share: Net income attributable to common stockholders 0.44 0.68 0.96 0.55 2014 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Operating revenues $ 679 $ 755 $ 846 $ 731 Operating income 187 255 337 224 Net income attributable to common stockholders 68 109 152 94 Basic earnings per share: Net income attributable to common stockholders 0.38 0.61 0.85 0.52 Diluted earnings per share: Net income attributable to common stockholders 0.38 0.61 0.85 0.52

Significant Accounting Polici31

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of American Water and all of its subsidiaries in which a controlling interest is maintained after the elimination of intercompany accounts and transactions. Intercompany balances and transactions between subsidiaries have been eliminated. The Company uses the equity method to report its investments in joint ventures in which the Company holds up to a 50% voting interest and cannot exercise control over the operations and policies of the investments. Under the equity method, the Company records its interests as an investment and its percentage share of the investee’s earnings as earnings or losses. In July 2015, the Company acquired a ninety-five percent interest in Water Solutions Holdings, LLC, including its wholly-owned subsidiary, Keystone Clearwater Solutions, LLC (collectively referred to as “Keystone”). The outside stockholders’ interest, which is redeemable at the option of the minority owners, is recognized as redeemable noncontrolling interest. The redeemable noncontrolling interest amounted to $7 as of December 31, 2015 and is included in other long-term liabilities in the accompanying Consolidated Balance Sheets. The net loss attributable to the noncontrolling interest was not significant. The Company has entered into an agreement, whereby it has the option to acquire from the minority owners, and the minority owners have the option to sell to the Company, the remaining five percent interest at fair value upon the occurrence of certain triggering events or at defined dates of December 31, 2016 and December 31, 2018.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates. The Company considers its critical accounting estimates to include: the application of regulatory accounting principles and the related determination and estimates of regulatory assets and liabilities; estimates used in impairment testing of goodwill and other long-lived assets, including regulatory assets; revenue recognition; accounting for income taxes; benefit plan assumptions; and contingent liabilities. The Company’s critical accounting estimates that are particularly sensitive to change in the near term are amounts reported for regulatory assets and liabilities, benefit plans assumptions, contingency-related obligations and goodwill.
Regulation	Regulation The Company’s regulated utilities are subject to economic regulation by the public utility commissions and the local governments of the states in which they operate (the “PUCs”). These PUCs generally authorize revenue at levels intended to recover the estimated costs of providing service, plus a return on net investments, or rate base. Regulators may also impose certain penalties or grant certain incentives. Due to timing and other differences in the collection of utility revenue, an incurred cost that would otherwise be charged to expense by a non-regulated entity is to be deferred as a regulatory asset if it is probable that the cost is recoverable in future rates. Conversely, GAAP requires recording of a regulatory liability for amounts collected in rates to recover costs expected to be incurred in the future or amounts collected in excess of costs incurred and refundable to customers. See Note 6—Regulatory Assets and Liabilities.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment consist primarily of utility plant. Additions to utility plant and replacements of retirement units of property are capitalized. Costs include material, direct labor and such indirect items as engineering and supervision, payroll taxes and benefits, transportation and an allowance for funds used during construction (“AFUDC”). The cost of repairs, maintenance, including planned major maintenance activities, and minor replacements is charged to maintenance expense as incurred. The costs incurred to acquire and internally develop computer software for internal use are capitalized as a unit of property. The carrying value of these costs amounted to $311 and $320 as of December 31, 2015 and 2014, respectively. When units of property are replaced, retired or abandoned, the recorded value is credited to the asset account and charged to accumulated depreciation. To the extent the Company recovers cost of removal or other retirement costs through rates after the retirement costs are incurred, a regulatory asset is recorded. In some cases, the Company recovers retirement costs through rates during the life of the associated asset and before the costs are incurred. These amounts result in a regulatory liability being reported based on the amounts previously recovered through customer rates, until the costs to retire those assets are incurred. The cost of property, plant and equipment is depreciated using the straight-line average remaining life method. The Company’s regulated utility subsidiaries record depreciation in conformity with amounts approved by state regulators after regulatory review of information the Company submits to support its estimates of the assets’ remaining useful lives. Nonutility property consists primarily of buildings and equipment utilized by the Company for internal operations. This property is stated at cost, net of accumulated depreciation calculated using the straight-line method over the useful lives of the assets.
Cash and Cash Equivalents	Cash and Cash Equivalents Substantially all cash is invested in interest-bearing accounts. All highly liquid investments with a maturity of three months or less when purchased are considered to be cash equivalents.
Restricted Funds	Restricted Funds Restricted funds primarily represent proceeds from financings for the construction and capital improvement of facilities and deposits for future services under operation and maintenance projects. The proceeds from these financings are held in escrow until the designated expenditures are incurred. Classification of restricted funds in the Consolidated Balance Sheets as either current or long-term is based upon the intended use of the funds.
Accounts Receivable and Unbilled Revenues	Accounts Receivable and Unbilled Revenues Accounts receivable include regulated utility customer accounts receivable, which represent amounts billed to water and wastewater customers on a cycle basis. Credit is extended based on the guidelines of the applicable PUCs and collateral is generally not required. Also included are market-based trade accounts receivable and nonutility customer receivables of the regulated subsidiaries. Unbilled revenues are accrued when service has been provided but has not been billed to customers.
Allowance for Uncollectible Accounts	Allowance for Uncollectible Accounts Allowances for uncollectible accounts are maintained for estimated probable losses resulting from the Company’s inability to collect receivables from customers. Accounts that are outstanding longer than the payment terms are considered past due. A number of factors are considered in determining the allowance for uncollectible accounts, including the length of time receivables are past due and previous loss history. The Company generally writes off accounts when they become uncollectible or are over a certain number of days outstanding. See Note 5—Allowance for Uncollectible Accounts.
Materials and Supplies	Materials and Supplies Materials and supplies are stated at the lower of cost or net realizable value. Cost is determined using the average cost method.
Goodwill	Goodwill Goodwill represents the excess of the purchase price paid over the estimated fair value of the assets acquired and liabilities assumed in the acquisition of a business. Goodwill is not amortized, but is tested for impairment at least annually or on an interim basis if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying value. Goodwill is primarily associated with the acquisitions of E’town Corporation in 2001, American Water in 2003 and Keystone in 2015 (the “Acquisitions”) and has been assigned to reporting units based on the fair values at the date of the Acquisitions. The reporting units in the Regulated Businesses segment are aggregated into a single reporting unit. The Market-Based Businesses is comprised of four non-reportable operating segments. The Company’s annual impairment test is performed as of November 30 of each year, in conjunction with the completion of the Company’s annual business plan. The Company assesses qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. If based on qualitative factors, the fair value of the reporting unit is more likely than not greater than the carrying amount, no further testing is required. If the Company bypasses the qualitative assessment or performs the qualitative assessment, but determines that it is more likely than not that its fair value is less than its carrying amount, a quantitative two-step, fair value-based test is performed. The first step compares the estimated fair value of the reporting unit to its respective net carrying value, including goodwill, on the measurement date. If the estimated fair value of any reporting unit is less than such reporting unit’s carrying value, then the second step is performed to measure the amount of the impairment loss (if any) for such reporting unit. The second step requires an allocation of fair value to the individual assets and liabilities using purchase price allocation accounting guidance in order to determine the implied fair value of goodwill. If the implied fair value of goodwill is less than the carrying amount for the reporting unit, an impairment loss is recorded as a reduction to goodwill and a charge to operating expense. Application of the goodwill impairment test requires management judgment, including the identification of reporting units and determining the fair value of the reporting unit. Management estimates fair value using a combination of a discounted cash flow analysis and market multiples analysis. Significant assumptions used in these fair value analyses include discount and growth rates and projected terminal values. The Company believes the assumptions and other considerations used to value goodwill to be appropriate. However, if experience differs from the assumptions and considerations used in its analysis, the resulting change could have a material adverse impact on the consolidated financial statements.
Long-Lived Assets	Long-Lived Assets Long-lived assets include land, buildings, equipment and long-term investments. Long-lived assets, other than investments and land, are depreciated over their estimated useful lives, and are reviewed for impairment whenever changes in circumstances indicate the carrying value of the asset may not be recoverable. Such circumstances would include items such as a significant decrease in the market value of a long-lived asset, a significant adverse change in the manner the asset is being used or planned to be used or in its physical condition, or a history of operating or cash flow losses associated with the use of the asset. In addition, changes in the expected useful life of these long-lived assets may also be an impairment indicator. When such events or changes occur, the Company estimates the fair value of the asset from future cash flows expected to result from the use and, if applicable, the eventual disposition of the asset and compares that to the carrying value of the asset. If the carrying value is greater than the fair value, an impairment loss is recorded. The Company believes the assumptions and other considerations used to evaluate the carrying value of long-lived assets are appropriate. However, if actual experience differs from the assumptions and considerations used in its estimates, the resulting change could have a material adverse impact on the consolidated financial statements. The key variables to determine fair value include assumptions regarding sales volume, rates, operating costs, labor and other benefit costs, capital additions, assumed discount rates and other economic factors. These variables require significant management judgment and include inherent uncertainties, since they are forecasting future events. If such assets are considered impaired, an impairment loss is recognized equal to the amount by which the asset’s carrying value exceeds its fair value. The long-lived assets of the regulated utility subsidiaries are tested on a separate entity basis for impairment testing as they are integrated state-wide operations that do not have the option to curtail service and generally have uniform tariffs. A regulatory asset is charged to earnings if and when future recovery in rates of that asset is no longer probable. The Company holds other investments including investments in privately held companies and investments in joint ventures accounted for using the equity method. The Company’s investments in privately held companies and joint ventures are classified as other long-term assets in the accompanying Consolidated Balance Sheets. The fair values of long-term investments are dependent on the financial performance and solvency of the entities in which the Company invests, as well as volatility inherent in the external markets. If such assets are considered impaired, an impairment loss is recognized equal to the amount by which the asset’s carrying value exceeds its fair value.
Advances for Construction and Contributions in Aid of Construction	Advances for Construction and Contributions in Aid of Construction Regulated utility subsidiaries may receive advances for construction and contributions in aid of construction from customers, home builders and real estate developers to fund construction necessary to extend service to new areas. Advances are refundable for limited periods of time as new customers begin to receive service or other contractual obligations are fulfilled. Included in other current liabilities as of December 31, 2015 and 2014 in the accompanying Consolidated Balance Sheets are estimated refunds of $19 and $18, respectively. Those amounts represent expected refunds during the next 12-month period. Advances that are no longer refundable are reclassified to contributions. Contributions are permanent collections of plant assets or cash for a particular construction project. For ratemaking purposes, the amount of such contributions generally serves as a rate base reduction since the contributions represent non-investor supplied funds. Generally, the Company depreciates utility plant funded by contributions and amortizes its contributions balance as a reduction to depreciation expense, producing a result which is functionally equivalent to reducing the original cost of the utility plant for the contributions. In accordance with applicable regulatory guidelines, some of the Company’s utility subsidiaries do not amortize contributions, and any contribution received remains on the balance sheet indefinitely. Amortization of contributions in aid of construction was $26, $24 and $22 for the years ended December 31, 2015, 2014 and 2013, respectively.
Recognition of Revenues	Recognition of Revenues Revenues of the regulated utility subsidiaries are recognized as water and wastewater services are provided, and include amounts billed to customers on a cycle basis and unbilled amounts based on estimated usage from the date of the meter reading associated with the latest customer bill to the end of the accounting period. The Company has agreements with the U.S. Department of Defense to operate and maintain water and wastewater systems at various military bases pursuant to 50-year contracts (“military agreements”). These contracts also include construction components that are accounted for separately from the O&M components. Nine of the military agreements are subject to periodic price redetermination adjustments and modifications for changes in circumstance. The remaining three agreements are subject to annual price adjustments under a mechanism similar to price redeterminations. Additionally, the Company has agreements ranging in length from two to 40 years with municipalities and businesses in various industries to operate and maintain water and wastewater systems (“O&M agreements”). Revenues from operations and management services are recognized as services are provided. See Note 15—Commitments and Contingencies. Revenues from construction projects are recognized over the contract term based on the costs incurred to date during the period compared to the total estimated costs over the entire contract. Losses on contracts are recognized during the period in which the loss first becomes probable and estimable. Revenues recognized during the period in excess of billings on construction contracts are recorded as unbilled revenue. Billings in excess of revenues recognized on construction contracts are recorded as other current liabilities until the recognition criteria are met. Changes in contract performance and related estimated contract profitability may result in revisions to costs and revenues and are recognized in the period in which revisions are determined.
Income Taxes	Income Taxes American Water and its subsidiaries participate in a consolidated federal income tax return for U.S. tax purposes. Members of the consolidated group are charged with the amount of federal income tax expense determined as if they filed separate returns. Certain income and expense items are accounted for in different time periods for financial reporting than for income tax reporting purposes. The Company provides deferred income taxes on the difference between the tax basis of assets and liabilities and the amounts at which they are carried in the financial statements. These deferred income taxes are based on the enacted tax rates expected to be in effect when these temporary differences are projected to reverse. In addition, the regulated utility subsidiaries recognize regulatory assets and liabilities for the effect on revenues expected to be realized as the tax effects of temporary differences, previously flowed through to customers, reverse. Investment tax credits have been deferred by the regulated utility subsidiaries and are being amortized to income over the average estimated service lives of the related assets. The Company recognizes accrued interest and penalties related to tax positions as a component of income tax expense and accounts for sales tax collected from customers and remitted to taxing authorities on a net basis.
Allowance for Funds Used During Construction	Allowance for Funds Used During Construction AFUDC is a non-cash credit to income with a corresponding charge to utility plant that represents the cost of borrowed funds or a return on equity funds devoted to plant under construction. The regulated utility subsidiaries record AFUDC to the extent permitted by the PUCs. The portion of AFUDC attributable to borrowed funds is shown as a reduction of interest, net in the accompanying Consolidated Statements of Operations. Any portion of AFUDC attributable to equity funds would be included in other income (expenses) in the accompanying Consolidated Statements of Operations. AFUDC is summarized in the following table for the years ended December 31: 2015 2014 2013 Allowance for other funds used during construction $ 13 $ 9 $ 13 Allowance for borrowed funds used during construction 8 6 6
Environmental Costs	Environmental Costs The Company’s water and wastewater operations are subject to U.S. federal, state, local and foreign requirements relating to environmental protection, and as such, the Company periodically becomes subject to environmental claims in the normal course of business. Environmental expenditures that relate to current operations or provide a future benefit are expensed or capitalized as appropriate. Remediation costs that relate to an existing condition caused by past operations are accrued, on an undiscounted basis, when it is probable that these costs will be incurred and can be reasonably estimated. Remediation costs accrued amounted to $1 and $2 as of December 31, 2015 and 2014, respectively. The accrual relates entirely to a conservation agreement entered into by a subsidiary of the Company with the National Oceanic and Atmospheric Administration (“NOAA”) requiring the Company to, among other provisions, implement certain measures to protect the steelhead trout and its habitat in the Carmel River watershed in the State of California. The Company has agreed to pay $1 annually from 2010 to 2016. The Company’s inception-to-date costs related to the NOAA agreement were recorded in regulatory assets in the accompanying Consolidated Balance Sheets as of December 31, 2015 and 2014 and are expected to be fully recovered from customers in future rates.
Derivative Financial Instruments	Derivative Financial Instruments The Company uses derivative financial instruments for purposes of hedging exposures to fluctuations in interest rates. These derivative contracts are entered into for periods consistent with the related underlying exposures and do not constitute positions independent of those exposures. The Company does not enter into derivative contracts for speculative purposes and does not use leveraged instruments. All derivatives are recognized on the balance sheet at fair value. On the date the derivative contract is entered into, the Company may designate the derivative as a hedge of the fair value of a recognized asset or liability (fair-value hedge) or a hedge of a forecasted transaction or of the variability of cash flows to be received or paid related to a recognized asset or liability (cash-flow hedge). Changes in the fair value of a fair-value hedge, along with the gain or loss on the underlying hedged item, are recorded in current-period earnings. The effective portion of gains and losses on cash-flow hedges are recorded in other comprehensive income, until earnings are affected by the variability of cash flows. Any ineffective portion of designated hedges is recognized in current-period earnings. Cash flows from derivative contracts are included in net cash provided by operating activities in the accompanying Consolidated Statements of Cash Flows.
New Accounting Standards	New Accounting Standards The following recently issued accounting standards have been adopted by the Company as of December 31, 2015: Standard Description Date of Adoption Application Effect on the Consolidated Financial Statements (or Other Significant Matters) Service Concession Arrangements Clarified that an operating entity should not account for a services concession arrangement with a public-sector grantor as a lease if: (1) the grantor controls or has the ability to modify or approve the services the operating entity must provide, to whom it must provide them, and at what price; and (2) the grantor controls any residual interest in the infrastructure at the end of the arrangement. In addition, the infrastructure used in a service concession arrangement would not be recognized as property, plant and equipment of the operating entity. January 1, 2015 Modified retrospective basis The Company reduced nonutility property and other long-term assets for infrastructure related to service concession arrangements and recognized a cumulative effect adjustment of $8 net of tax, to the opening balance of accumulated deficit at January 1, 2015. Reporting Discontinued Operations Amended the criteria for determining which disposals can be presented as discontinued operations and modified related disclosure requirements. Now, a discontinued operation is defined as a component or group of components that is disposed of or is classified as held for sale and represents a strategic shift that has or will have a major effect on an entity’s operations and financial results. In addition, the update no longer precludes presentation as a discontinued operation if there are operations and cash flows of the component that have not been eliminated from the reporting entity’s ongoing operations or if there is significant continuing involvement with a component after its disposal. January 1, 2015 Prospective basis The adoption of this standard did not impact the Company’s results of operations, financial position or cash flows. Presentation of Debt Issuance Costs Updated guidance on the imputation of interest and simplified the presentation of debt issuance costs. The updated guidance requires that debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the related liability. Such treatment is consistent with the current presentation of debt discounts or premiums. October 1, 2015 Retrospective basis The December 31, 2014 Consolidated Balance Sheet was revised, which resulted in decreases of $7 to other assets and long-term debt, respectively. Unamortized debt issuance costs of $7 were included in long-term debt as of December 31, 2015. Presentation of Deferred Income Taxes Simplified the presentation of deferred income taxes and requires that deferred income tax assets and liabilities be classified as noncurrent in the balance sheet. October 1, 2015 Retrospective basis The December 31, 2014 Consolidated Balance Sheet was revised, which resulted in decreases of $87 to the current deferred income tax asset and long-term deferred income tax liability. The following recently issued accounting standards have not yet been adopted by the Company as of December 31, 2015: Standard Description Effective Date Application Effect on the Consolidated Financial Statements (or Other Significant Matters) Revenue from Contracts with Customers Provided new revenue recognition guidance that will replace most existing revenue recognition guidance in GAAP, including industry-specific guidance. Upon adoption, a company will recognize revenue for the transfer of goods or services to customers equal to the amount that it expects to be entitled to receive for those goods or services. The guidance also requires additional disclosures about the nature, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments. January 1, 2018 The Company is currently evaluating the alternative methods available and has not yet selected a transition method. The Company is currently evaluating the effect on the financial statements and related disclosures. Accounting for Fees Paid in a Cloud Computing Arrangement Clarified guidance on how customers should account for fees paid in a cloud computing arrangement. Under the new guidance, if a cloud computing arrangement contains a software license, the customer would account for the software license element of the arrangement consistent with the acquisition of other software licenses. If the cloud computing arrangement does not include a software license, the customer would account for the arrangement as a service contract. January 1, 2016 Prospective basis The effect on the financial statements upon adoption will be dependent on the software license arrangements entered into by the Company subsequent adoption.
Reclassifications	Reclassifications Certain reclassifications have been made to prior periods in the accompanying consolidated financial statements and notes to conform to the current presentation

Significant Accounting Polici32

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Schedule of Allowance for Funds Used During Construction	AFUDC is summarized in the following table for the years ended December 31: 2015 2014 2013 Allowance for other funds used during construction $ 13 $ 9 $ 13 Allowance for borrowed funds used during construction 8 6 6

Acquisitions and Divestitures (

Acquisitions and Divestitures (Tables)	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Summary of Discontinued Operations Presented in Consolidated Statements of Operations, Comprehensive Income	The following table summarizes the operating results of discontinued operations presented in the accompanying Consolidated Statements of Operations for the years ended December 31: 2014 2013 Operating revenues $ 13 $ 23 Total operating expenses, net 19 26 Loss from discontinued operations before income taxes (6 ) (3 ) Provision (benefit) for income taxes 1 (1 ) Loss from discontinued operations, net of tax $ (7 ) $ (2 )

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Summary of Major Classes of Property, Plant and Equipment by Category	The following table summarizes the major classes of property, plant and equipment by category as of December 31: Range of Remaining Weighted Average 2015 2014 Useful Lives Useful Life Utility plant: Land and other non-depreciable assets $ 141 $ 137 Sources of supply 705 681 12 to 127 Years 51 Years Treatment and pumping facilities 3,070 2,969 3 to 101 Years 39 Years Transmission and distribution facilities 8,516 7,963 9 to 156 Years 83 Years Services, meters and fire hydrants 3,250 3,062 8 to 93 Years 35 Years General structures and equipment 1,227 1,096 1 to 154 Years 39 Years Waste treatment, pumping and disposal 313 281 2 to 115 Years 46 Years Waste collection 473 399 5 to 109 Years 56 Years Construction work in progress 404 303 Total utility plant 18,099 16,891 Nonutility property 405 378 3 to 50 years 6 Years Total property, plant and equipment $ 18,504 $ 17,269

Allowance for Uncollectible A35

Allowance for Uncollectible Accounts (Tables)	12 Months Ended
	Dec. 31, 2015
Financing Receivable Allowance For Credit Loss Additional Information [Abstract]
Schedule of Allowances for Uncollectible Accounts	The following table summarizes the changes in the Company’s allowances for uncollectible accounts for the years ended December 31: 2015 2014 2013 Balance as of January 1 $ (35 ) $ (34 ) $ (27 ) Amounts charged to expense (32 ) (37 ) (27 ) Amounts written off 38 43 24 Recoveries of amounts written off (10 ) (7 ) (4 ) Balance as of December 31 $ (39 ) $ (35 ) $ (34 )

Regulatory Assets and Liabili36

Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Regulatory Assets And Liabilities Disclosure [Abstract]
Summary of Composition of Regulatory Assets	The regulatory assets represent costs that are probable of recovery from customers in future rates. The majority of the regulatory assets earn a return. The following table summarizes the composition of regulatory assets as of December 31: 2015 2014 Deferred pension expense $ 269 $ 263 Income taxes recoverable through rates 236 229 Removal costs recoverable through rates 225 163 Deferred other postretirement benefit expense 90 107 San Clemente Dam project costs 95 72 Regulatory balancing accounts 88 60 Debt expense 68 71 Purchase premium recoverable through rates 60 60 Deferred tank painting costs 37 37 Other 103 91 Total Regulatory Assets $ 1,271 $ 1,153
Summary of Composition of Regulatory Liabilities	The following table summarizes the composition of regulatory liabilities as of December 31: 2015 2014 Removal costs recovered through rates $ 311 $ 301 Pension and other postretirement benefit balancing accounts 59 54 Other 32 37 Total Regulatory Liabilities $ 402 $ 392

Goodwill and Other Intangible37

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Changes in Goodwill Assets	Goodwill The following table summarizes changes in the carrying amount of goodwill for the years ended December 31, 2015 and 2014: Regulated Businesses Market-Based Businesses Consolidated Cost Accumulated Impairment Cost Accumulated Impairment Cost Accumulated Impairment Total Net Balance as of January 1, 2014 $ 3,412 $ (2,332 ) $ 236 $ (108 ) $ 3,648 $ (2,440 ) $ 1,208 Goodwill from acquisitions 3 — 91 — 94 — 94 Balance as of December 31, 2015 $ 3,415 $ (2,332 ) $ 327 $ (108 ) $ 3,742 $ (2,440 ) $ 1,302

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	The following table presents changes in accumulated other comprehensive loss by component, net of tax, for the years ended December 31, 2015 and 2014: Defined Benefit Plans Accumulated Employee Benefit Plan Funded Status Amortization of Prior Service Cost Amortization of Actuarial Loss Foreign Currency Translation Loss on Cash Flow Hedge Other Beginning balance as of January 1, 2014 $ (70 ) $ 1 $ 31 $ 3 $ — $ (35 ) Other comprehensive loss (income) (46 ) — — — (1 ) (47 ) Ending balance as of December 31, 2014 $ (116 ) $ 1 $ 31 $ 3 $ (1 ) $ (82 ) Other comprehensive loss (income) (10 ) — 5 (1 ) — (6 ) Ending balance as of December 31, 2015 $ (126 ) $ 1 $ 36 $ 2 $ (1 ) $ (88 )

Stock Based Compensation (Table

Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	The Company recognizes compensation expense for stock awards over the vesting period of the award. The following table presents stock-based compensation expense recorded in operation and maintenance expense in the accompanying Consolidated Statements of Operations for the years ended December 31: 2015 2014 2013 Stock options $ 2 $ 2 $ 3 RSUs 8 10 9 ESPP 1 1 1 Stock-based compensation 11 13 13 Income tax benefit (4 ) (5 ) (5 ) Stock-based compensation expense, net of tax $ 7 $ 8 $ 8
Summary of Weighted Average Assumptions	The following table summarizes the weighted-average assumptions used in the Black-Scholes option-pricing model for grants and the resulting weighted-average grant date fair value per share of stock options granted for the years ended December 31: 2015 2014 2013 Dividend yield 2.35 % 2.55 % 2.52 % Expected volatility 17.64 % 17.75 % 23.50 % Risk-free interest rate 1.48 % 1.06 % 0.70 % Expected life (years) 4.4 3.6 4.3 Exercise price $ 52.75 $ 44.29 $ 39.60 Grant date fair value per share $ 6.21 $ 4.57 $ 5.78
Summary of Stock Option Activity	The table below summarizes stock option activity for the year ended December 31, 2015: Shares (in thousands) Weighted-Average Exercise Price (per share) Weighted-Average Remaining Life (years) Aggregate Intrinsic Value Options outstanding as January 1, 2015 1,910 $ 33.47 3.9 $ 38 Granted 301 52.75 Forfeited or expired (51 ) 44.36 Exercised (973 ) 31.26 Options outstanding as of December 31, 2015 1,187 $ 39.70 3.9 $ 24 Exercisable as of December 31, 2015 666 $ 32.92 2.6 $ 18
Weighted-Average Assumptions used in Monte Carlo Simulation and Weighted-Average Grant Date Fair Value of Restricted Stock Units Granted	The following table presents the weighted-average assumptions used in the Monte Carlo simulation and the weighted-average grant date fair values of RSUs granted for the years ended December 31: 2015 2014 2013 Expected volatility 14.93 % 17.78 % 19.37 % Risk-free interest rate 1.07 % 0.75 % 0.40 % Expected life (years) 3.0 3.0 3.0 Grant date fair value per share $ 62.10 $ 45.45 $ 40.13 The table below summarizes restricted stock unit activity for the year ended December 31, 2015: Shares (in thousands) Weighted-Average Grant Date Fair Value (per share) Non-vested total as of January 1, 2015 516 $ 41.46 Granted 156 55.67 Performance share adjustment 93 38.11 Vested (304 ) 39.46 Forfeited (25 ) 45.84 Non-vested total as of December 31, 2015 436 $ 46.97
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional Information to Stock Options Activity	The following table summarizes additional information regarding stock options exercised during the years ended December 31: 2015 2014 2013 Intrinsic value $ 22 $ 13 $ 15 Exercise proceeds 30 15 20 Income tax benefit 7 4 4
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional Information to Stock Options Activity	The following table summarizes additional information regarding RSUs distributed during the years ended December 31: 2015 2014 2013 Intrinsic value $ 17 $ 16 $ 14 Income tax benefit 2 2 2

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Components of Long-Term Debt	The Company obtains long-term debt primarily to fund capital expenditures of the regulated subsidiaries and refinance debt of the parent company. The following table summarizes the components of long-term as of December 31: Rate Weighted Average Rate Maturity 2015 2014 Long-term debt of American Water Capital Corp. (a) Senior notes — 3.40%-8.27% 5.23% 2016-2045 $ 4,273 $ 3,753 Private activity bonds and government funded debt — 1.79%-6.25% 5.41% 2021-2040 195 231 Long-term debt of other American Water subsidiaries Private activity bonds and government funded debt — (b) 0.00%-6.20% 4.70% 2016-2041 790 795 Mortgage bonds — fixed rate 4.29%-9.71% 7.41% 2017-2039 637 677 Mandatorily redeemable preferred stock 8.47%-9.75% 8.61% 2019-2036 13 17 Capital lease obligations 12.23% 12.23% 2026 1 1 Long-term debt 5,909 5,474 Unamortized debt premium, net (c) 23 31 Unamortized debt issuance costs (7 ) (6 ) Interest rate swap fair value adjustment 3 4 Total long-term debt $ 5,928 $ 5,503 (a) This indebtedness is considered “debt” for purposes of a support agreement between American Water and American Water Capital Corp. (“AWCC”), which serves as a functional equivalent of a guarantee by AWCC’s payment obligations under such indebtedness. (b) Includes $8 and $10 of variable rate debt with variable-to-fixed interest rate swaps ranging between 4.65% and 3.93%, as of December 31, 2015 and 2014, respectively. This debt was assumed via an acquisition in 2013. (c) Primarily fair value adjustments previously recognized in acquisition purchase accounting.
Future Sinking Fund Payments and Maturities	The future sinking fund payments and maturities were as follows: Year Amount 2016 $ 54 2017 573 2018 457 2019 166 2020 22 Thereafter 4,637
Long-Term Debt Issued	The following long-term debt was issued in 2015: Company Type Rate Maturity Amount AWCC Senior notes—fixed rate 3.40%-4.30% 2025-2045 $ 550 Other American Water subsidiaries Private activity bonds and government funded debt — 1.00%-1.56% 2032 15 Total issuances $ 565
Long-Term Debt Retired Through Sinking Fund Payments and Maturities	The following long-term debt was retired through optional redemption or payment at maturity during 2015: Company Type Rate Maturity Amount AWCC Private activity bonds and government funded debt—fixed rate 1.79%-5.25% 2015-2031 $ 36 AWCC Senior notes — 6.00% 2015 30 Other American Water subsidiaries (a) Private activity bonds and government funded debt — 0.00%-5.40% 2015-2041 61 Other American Water subsidiaries Mandatorily redeemable preferred stock 8.49%-9.18% 2031-2036 4 Total retirements and redemptions $ 131 (a) Includes $2 of non-cash defeasance via the use of restricted funds.
Balance Sheet Classification	The following table provides a summary of the derivative and fixed rate debt fair value balances recorded by the Company as of December 31, 2015 and 2014, and the line items in the Consolidated Balance Sheets in which such amounts are recorded: Balance Sheet Classification 2015 2014 Regulatory and other long-term assets Other $ 2 $ 4 Long-term debt Long-term debt 2 4
Income Statement Classification	For derivative instruments that are designated and qualify as fair-value hedges, the gain or loss on the hedge instrument as well as the offsetting gain or loss on the hedged item attributable to the hedged risk are recognized in current net income. The Company includes the gain or loss on the derivative instrument and the offsetting gain or loss on the hedged item in interest expense for the years ended December 31 were as follows: Income Statement Classification 2015 2014 2013 Interest, net Loss on swap $ (1 ) $ (1 ) $ (3 ) Gain on borrowing 1 1 3

Short-Term Debt (Tables)

Short-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Short Term Borrowings [Abstract]
Schedule of Company's Aggregate Credit Facility Commitments, Letter of Credit Sub-Limit Under Revolving Credit Facility and Commercial Paper Limit and Available Capacity	The following table summarizes the Company’s aggregate credit facility commitments, letter of credit sub-limit under our revolving credit facility and commercial paper limit, as well as the available capacity for each as of: Available Available Available Credit Facility Credit Facility Letter of Credit Letter of Credit Commercial Paper Commercial Paper Commitment Capacity Sublimit (a) Capacity Limit Capacity December 31, 2015 $ 1,266 $ 1,182 $ 150 $ 68 $ 1,000 $ 374 December 31, 2014 1,250 1,212 150 112 1,000 550
Schedule Of Short-Term Borrowings Activity	The following table summarizes the short-term borrowing activity for AWCC for the years ended December 31: 2015 2014 Average borrowings $ 553 $ 549 Maximum borrowings outstanding 871 745 Weighted average interest rates, computed on daily basis 0.49 % 0.31 % Weighted average interest rates, as of December 31 0.66 % 0.42 %

General Taxes (Tables)

General Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
General Tax
Components of General Tax Expense from Continuing Operations	The following table summarizes the components of general tax expense from continuing operations for the years ended December 31: 2015 2014 2013 Gross receipts and franchise $ 99 $ 96 $ 96 Property and capital stock 98 96 94 Payroll 31 31 31 Other general 15 13 13 Total general taxes $ 243 $ 236 $ 234

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Components of Income Tax Expense from Continuing Operations	The following table summarizes the components of income tax expense from continuing operations for the years ended December 31: 2015 2014 2013 Current income taxes State $ 10 $ 11 $ 7 Federal — 15 (20 ) Total current income taxes $ 10 $ 26 $ (13 ) Deferred income taxes State $ 32 $ 31 $ 27 Federal 265 224 225 Amortization of deferred investment tax credits (1 ) (1 ) (2 ) Total deferred income taxes 296 254 250 Provision for income taxes $ 306 $ 280 $ 237
Reconciliation of Income Tax Expense from Continuing Operations	The following is a reconciliation between the statutory federal income tax rate and the Company’s effective tax rate for the years ended December 31: 2015 2014 2013 Income tax at statutory rate 35.0 % 35.0 % 35.0 % Increases (decreases) resulting from: State taxes, net of federal taxes 3.6 3.8 3.6 Flow through differences 0.5 0.4 0.5 Amortization of deferred investment tax credits (0.1 ) (0.1 ) (0.3 ) Subsidiary preferred dividends — 0.1 0.2 Other, net 0.1 0.2 — Provision for income taxes 39.1 % 39.4 % 39.0 %
Components of Net Deferred Tax Liability from Continuing Operations	The following table provides the components of the net deferred tax liability from continuing operations as of December 31: 2015 2014 Deferred tax assets Advances and contributions $ 513 $ 502 Other postretirement benefits 76 105 Tax losses and credits 173 197 Pension benefits 105 125 Unamortized debt discount, net 20 20 Other 12 42 Total deferred tax assets 899 991 Valuation allowance (8 ) (10 ) Total deferred tax assets, net of allowance $ 891 $ 981 Deferred tax liabilities Property, plant and equipment, principally due to depreciation differences $ 2,913 $ 2,677 Income taxes recoverable through rates 76 76 Deferred other postretirement benefits 35 65 Deferred pension benefits 104 121 Other 73 76 Total deferred tax liabilities 3,201 3,015 Total deferred tax liabilities, net of deferred tax assets $ (2,310 ) $ (2,034 )
Changes in Gross Liability Excluding Interest and Penalties for Unrecognized Tax Benefits	The following table summarizes the changes in the Company’s gross liability, excluding interest and penalties, for unrecognized tax benefits: Balance as of January 1, 2014 $ 178 Increases in current period tax positions 54 Decreases in prior period measurement of tax positions (37 ) Balance as of December 31, 2014 $ 195 Increases in current period tax positions 39 Decreases in prior period measurement of tax positions (1 ) Balance as of December 31, 2015 $ 233
Changes in Valuation Allowance	The following table summarizes the changes in the Company’s valuation allowance: Balance as of January 1, 2013 $ 19 Decreases in current period tax positions (6 ) Balance as of December 31, 2013 $ 13 Decreases in current period tax positions (3 ) Balance as of December 31, 2014 $ 10 Decreases in current period tax positions (2 ) Balance as of December 31, 2015 $ 8

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Schedule of Significant Unobservable Inputs	The following tables present a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3) for 2015 and 2014, respectively: Level 3 Balance as of January 1, 2015 $ 127 Actual return on assets 12 Purchases, issuances and settlements, net (3 ) Balance as of December 31, 2015 $ 136 Level 3 Balance as of January 1, 2014 $ 44 Actual return on assets 7 Purchases, issuances and settlements, net 76 Balance as of December 31, 2014 $ 127
Schedule of Rollforward Changes in Benefit Obligation and Plan Assets	The following table provides a rollforward of the changes in the benefit obligation and plan assets for the most recent two years for all plans combined: Pension Benefits Other Benefits 2015 2014 2015 2014 Change in benefit obligation Benefit obligation as of January 1, $ 1,746 $ 1,494 $ 703 $ 562 Service cost 37 32 14 11 Interest cost 74 76 30 29 Plan participants' contributions — — 2 2 Actuarial (gain) loss (76 ) 256 (58 ) 123 Gross benefits paid (61 ) (112 ) (26 ) (26 ) Federal subsidy — — 2 2 Benefit obligation as of December 31, $ 1,720 $ 1,746 $ 667 $ 703 Change in plan assets Fair value of plan assets as of January 1, $ 1,428 $ 1,384 $ 512 $ 475 Actual return on plan assets (21 ) 116 (15 ) 49 Employer contributions 30 40 27 12 Plan participants' contributions — — 2 2 Benefits paid (61 ) (112 ) (26 ) (26 ) Fair value of plan assets as of December 31, $ 1,376 $ 1,428 $ 500 $ 512 Funded status as of December 31, $ (344 ) $ (318 ) $ (167 ) $ (191 ) Amounts recognized in the balance sheet consist of: Noncurrent asset $ — $ — $ 2 $ 1 Current liability (2 ) (2 ) — — Noncurrent liability (342 ) (316 ) (169 ) (192 ) Net amount recognized $ (344 ) $ (318 ) $ (167 ) $ (191 )
Summary of Accumulated Other Comprehensive Income and Regulatory Assets	The following table provides the components of the Company’s accumulated other comprehensive income and regulatory assets that have not been recognized as components of periodic benefit costs as of December 31: Pension Benefits Other Benefits 2015 2014 2015 2014 Net actuarial loss $ 397 $ 379 $ 97 $ 119 Prior service cost (credit) 3 4 (10 ) (12 ) Net amount recognized $ 400 $ 383 $ 87 $ 107 Regulatory assets $ 258 $ 248 $ 87 $ 107 Accumulated other comprehensive income 142 135 — — Total $ 400 $ 383 $ 87 $ 107
Schedule of Accumulated and Projected Benefit Obligations	As of December 31, 2015 and 2014, the projected benefit obligation, accumulated benefit obligation and fair value of plan assets for pension plans with a projected obligation in excess of plan assets were as follows: Projected Benefit Obligation Exceeds the Fair Value of Plans' Assets 2015 2014 Projected benefit obligation $ 1,721 $ 1,746 Fair value of plan assets 1,376 1,428 Accumulated Benefit Obligation Exceeds the Fair Value of Plans' Assets 2015 2014 Accumulated benefit obligation $ 1,584 $ 1,616 Fair value of plan assets 1,376 1,428
Schedule of Expected Cash Flows for Pension and Postretirement Benefit Plans	Information about the expected cash flows for the pension and postretirement benefit plans is as follows: Pension Other Benefits Benefits 2016 expected employer contributions To plan trusts $ 33 $ 22 To plan participants 2 —
Schedule of Expected Benefit Payments	The following table reflects the net benefits expected to be paid from the plan assets or the Company’s assets: Pension Benefits Other Benefits Expected Benefit Payments Expected Benefit Payments Expected Federal Subsidy Payments 2016 $ 65 $ 28 $ 2 2017 70 30 2 2018 76 32 2 2019 82 35 3 2020 89 37 3 2021-2025 525 212 18
Schedule of Significant Assumptions of Pension and Postretirement Benefit Plans	The significant assumptions related to the Company’s pension and other postretirement benefit plans were as follows: Pension Benefits Other Benefits 2015 2014 2013 2015 2014 2013 Weighted-average assumptions used to determine December 31 benefit obligations Discount rate 4.66% 4.24% 5.12% 4.67% 4.24% 5.10% Rate of compensation increase 3.10% 3.12% 3.15% N/A N/A N/A Medical trend N/A N/A N/A graded from graded from graded from 6.50% in 2015 6.75% in 2014 7.00% in 2013 to 5.00% in 2021+ to 5.00% in 2021+ to 5.00% in 2019+ Weighted-average assumptions used to determine net periodic cost Discount rate 4.24% 5.12% 4.17% 4.24% 5.10% 4.16% Expected return on plan assets 6.91% 6.91% 7.49% 4.92% 5.87% 6.99% Rate of compensation increase 3.12% 3.15% 3.19% N/A N/A N/A Medical trend N/A N/A N/A graded from graded from graded from 6.75% in 2015 7.00% in 2014 7.25% in 2013 to 5.00% in 2021+ to 5.00% in 2019+ to 5.00% in 2019+ N/A—Assumption is not applicable.
Schedule of Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates	Assumed health care cost trend rates have a significant effect on the amounts reported for the other postretirement benefit plans. The health care cost trend rate is based on historical rates and expected market conditions. A one-percentage-point change in assumed health care cost trend rates would have the following effects: One-Percentage-Point Increase One-Percentage-Point Decrease Effect on total of service and interest cost components $ 8 $ (6 ) Effect on other postretirement benefit obligation $ 99 $ (81 )
Components of Net Periodic Benefit Costs	The following table provides the components of net periodic benefit costs for the years ended December 31: 2015 2014 2013 Components of net periodic pension benefit cost Service cost $ 37 $ 32 $ 37 Interest cost 74 76 68 Expected return on plan assets (97 ) (95 ) (88 ) Amortization of: Prior service cost (credit) 1 1 1 Actuarial (gain) loss 25 — 37 Net periodic pension benefit cost $ 40 $ 14 $ 55 Other changes in plan assets and benefit obligations recognized in other comprehensive income Amortization of prior service credit (cost) $ — $ — $ — Current year actuarial (gain) loss 10 46 (73 ) Amortization of actuarial gain (loss) (5 ) — (9 ) Total recognized in other comprehensive income $ 5 $ 46 $ (82 ) Total recognized in net periodic benefit cost and comprehensive income $ 45 $ 60 $ (27 ) Components of net periodic other postretirement benefit cost Service cost $ 14 $ 11 $ 15 Interest cost 30 29 29 Expected return on plan assets (26 ) (28 ) (30 ) Amortization of: Prior service cost (credit) (2 ) (2 ) (2 ) Actuarial (gain) loss 5 — 11 Net periodic other postretirement benefit cost $ 21 $ 10 $ 23
Schedule of Estimated Amounts Amortized Accumulated other Comprehensive Income	The estimated amounts that will be amortized from accumulated other comprehensive income and regulatory assets into net periodic benefit cost in 2016 are as follows: Pension Benefits Other Benefits Actuarial (gain) loss $ 27 $ 3 Prior service cost (credit) 1 (2 ) Total $ 28 $ 1
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Schedule of Changes in Fair Value of Plan Assets	The fair values and asset allocations of pension plan assets as of December 31, 2015 and 2014, respectively, by asset category were as follows: Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Inputs Inputs as of Asset Category 2016 Total (Level 1) (Level 2) (Level 3) December 31, 2015 Cash — $ 5 $ 5 $ — $ — — Equity Securities: U.S. large cap 24 % 318 318 — — 23 % U.S. small cap 8 % 115 115 — — 8 % International 20 % 260 — 260 — 19 % Fixed Income Securities: 40 % 41 % U.S. Treasury and government bonds — 120 95 25 — — Corporate bonds — 375 — 375 — — Mortgage-backed securities — 9 — 9 — — Long duration bond fund — 7 7 — — — Guarantee annuity contracts — 49 — 8 41 — Real Estate 6 % 95 — — 95 7 % REITs 2 % 23 — 23 — 2 % Total 100 % $ 1,376 $ 540 $ 700 $ 136 100 % Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Inputs Inputs as of Asset Category 2015 Total (Level 1) (Level 2) (Level 3) December 31, 2014 Cash — $ 8 $ 8 $ — $ — — Equity Securities: U.S. large cap 24 % 342 342 — — 24 % U.S. small cap 8 % 117 117 — — 8 % International 20 % 274 — 274 — 19 % Fixed Income Securities: 40 % 41 % U.S. Treasury and government bonds — 140 121 19 — — Corporate bonds — 377 — 377 — — Mortgage-backed securities — 4 — 4 — — Long duration bond fund — 7 7 — — — Guarantee annuity contracts — 51 — 9 42 — Real Estate 6 % 85 — — 85 6 % REITs 2 % 23 — 23 — 2 % Total 100 % $ 1,428 $ 595 $ 706 $ 127 100 %
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Schedule of Changes in Fair Value of Plan Assets	The fair values and asset allocations of postretirement benefit plan assets as of December 31, 2015 and 2014, respectively, by asset category, were as follows: Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Inputs Inputs as of Asset Category 2016 Total (Level 1) (Level 2) (Level 3) December 31, 2015 Bargain VEBA: Equity Securities: U.S. large cap 9 % $ 32 $ 32 $ — $ — 9 % International 11 % 38 38 — — 10 % Fixed Income Securities: 80 % 81 % U.S. Treasury and government bonds — 118 118 — — — Corporate bonds — 184 — 184 — — Long duration bond fund — 3 3 — — — Future and option contracts (a) — 1 1 — — — Total Bargain VEBA 100 % $ 376 $ 192 $ 184 $ — 100 % Non-bargain VEBA: Cash — $ 2 $ 2 $ — $ — — Equity Securities: U.S. large cap 21 % 24 24 — — 21 % U.S. small cap 21 % 26 26 — — 22 % International 28 % 33 33 — — 28 % Fixed Income Securities: 30 % 29 % Core fixed income bond fund — 33 33 — — — Total Non-bargain VEBA 100 % $ 118 $ 118 $ — $ — 100 % Life VEBA: Equity Securities: U.S. large cap 70 % $ 4 $ 4 $ — $ — 68 % Fixed Income Securities: 30 % 32 % Core fixed income bond fund — 2 2 — — — Total Life VEBA 100 % $ 6 $ 6 $ — $ — 100 % Total 100 % $ 500 $ 316 $ 184 $ — 100 % (a) Includes cash for margin requirements. Quoted Prices in Active Significant Significant Percentage Target Markets for Observable Unobservable of Plan Assets Allocation Identical Assets Inputs Inputs as of Asset Category 2015 Total (Level 1) (Level 2) (Level 3) December 31, 2014 Bargain VEBA: Equity Securities: U.S. large cap 9 % $ 34 $ 34 $ — $ — 9 % International 11 % 41 41 — — 10 % Fixed Income Securities: 80 % 81 % U.S. Treasury and government bonds — 155 155 — — — Corporate bonds — 168 — 168 — — Long duration bond fund — 3 3 — — — Future and option contracts (a) — 1 1 — — — Total Bargain VEBA 100 % $ 402 $ 234 $ 168 $ — 100 % Non-bargain VEBA: Cash — $ 1 $ 1 $ — $ — — Equity Securities: U.S. large cap 21 % 22 22 — — 21 % U.S. small cap 21 % 21 21 — — 21 % International 28 % 28 28 — — 28 % Fixed Income Securities: 30 % 30 % Core fixed income bond fund — 31 31 — — — Total Non-bargain VEBA 100 % $ 103 $ 103 $ — $ — 100 % Life VEBA: Equity Securities: U.S. large cap 70 % $ 5 $ 5 $ — $ — 67 % Fixed Income Securities: 30 % 33 % Core fixed income bond fund — 2 2 — — — Total Life VEBA 100 % $ 7 $ 7 $ — $ — 100 % Total 100 % $ 512 $ 344 $ 168 $ — 100 % (a) Includes cash for margin requirements.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Summary of Future Annual Commitments Related to Minimum Quantities of Purchased Water Having Non-Cancelable Terms	The Company’s regulated subsidiaries maintain agreements with other water purveyors for the purchase of water to supplement their water supply. The future annual commitments related to minimum quantities of purchased water having non-cancelable terms are as follows: Year Amount 2016 $ 51 2017 45 2018 44 2019 43 2020 44 Thereafter 383

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Reconciliation of Numerator and Denominator for Basic and Diluted Earnings Per Share	The following is a reconciliation of the numerator and denominator for basic and diluted earnings per share (“EPS”) calculations for the years ended December 31: 2015 2014 2013 Numerator Income from continuing operations $ 476 $ 430 $ 371 Loss from discontinued operations, net of tax — (7 ) (2 ) Net income available to common stockholders $ 476 $ 423 $ 369 Denominator Weighted average common shares outstanding — 179 179 178 Effect of dilutive common stock equivalents 1 1 1 Weighted average common shares outstanding—Diluted 180 180 179

Fair Values of Financial Inst47

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Carrying Amounts and Fair Values of Financial Instruments	The carrying amounts, including fair value adjustments previously recognized in acquisition purchase accounting and a fair value adjustment related to the Company’s interest rate swap fair value hedge (which is classified as Level 2 in the fair value hierarchy), and fair values of the financial instruments were as follows: Carrying December 31, 2015 Amount L e Level 2 Level 3 Total Preferred stock with mandatory redemption requirements $ 13 $ — $ — $ 18 $ 18 Long-term debt (excluding capital lease obligations) 5,914 3,397 1,419 1,941 6,757 Carrying December 31, 2014 Amount Level 1 Level 2 Level 3 Total Preferred stock with mandatory redemption requirements $ 17 $ — $ — $ 22 $ 22 Long-term debt (excluding capital lease obligations) 5,485 2,874 1,475 2,055 6,404
Fair Value Measurements of Assets and Liabilities on Recurring Basis	Recurring Fair Value Measurements The following table presents assets and liabilities measured and recorded at fair value on a recurring basis and their level within the fair value hierarchy as of December 31, 2015 and 2014, respectively: December 31, 2015 Level 1 Level 2 Level 3 Total Assets Restricted funds $ 27 $ — $ — $ 27 Rabbi trust investments 12 12 Deposits 1 — — 1 Mark-to-market derivative asset — 2 — 2 Other investments 4 — — 4 Total assets 44 2 — 46 Liabilities Deferred compensation obligation 11 — — 11 Mark-to-market derivative liability — 1 — 1 Total liabilities 11 1 — 12 Total net assets $ 33 $ 1 $ — $ 34 December 31, 2014 Level 1 Level 2 Level 3 Total Assets Restricted funds $ 23 $ — $ — $ 23 Rabbi trust investments — 12 — 12 Deposits 4 — — 4 Mark-to-market derivative asset — 4 — 4 Other investments 22 — — 22 Total assets 49 16 — 65 Liabilities Deferred compensation obligation — 12 — 12 Mark-to-market derivative liability — 1 — 1 Total liabilities — 13 — 13 Total net assets $ 49 $ 3 $ — $ 52

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2015
Leases [Abstract]
Schedule of Minimum Annual Future Rental Commitment Under Operating Leases	The minimum annual future rental commitment under operating leases that have initial or remaining non-cancelable lease terms over the next five years and thereafter are as follows: Year Amount 2016 $ 13 2017 12 2018 11 2019 10 2020 8 Thereafter 74

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Summarized Segment Information	2015 Regulated Businesses Market-Based Businesses Other Consolidated Operating revenues $ 2,743 $ 434 $ (18 ) $ 3,159 Depreciation and amortization 411 8 21 440 Total operating expenses, net 1,732 370 (18 ) 2,084 Interest, net 248 (2 ) 62 308 Income from continuing operations before income taxes 776 68 (62 ) 782 Provision for income taxes 303 26 (23 ) 306 Income from continuing operations 473 42 (39 ) 476 Total assets 15,258 496 1,487 17,241 Capital expenditures 1,143 17 — 1,160 2014 Regulated Businesses Market-Based Businesses Other Consolidated Operating revenues $ 2,674 $ 355 $ (18 ) $ 3,011 Depreciation and amortization 394 6 24 424 Total operating expenses, net 1,726 300 (18 ) 2,008 Interest, net 248 (2 ) 53 299 Income from continuing operations before income taxes 707 58 (55 ) 710 Provision for income taxes 273 18 (11 ) 280 Income from continuing operations 434 40 (44 ) 430 Total assets (b) 14,343 314 1,381 16,038 Capital expenditures 946 10 — 956 2013 Regulated Businesses Market-Based Businesses Other Consolidated Operating revenues (a) $ 2,594 $ 303 $ (18 ) $ 2,879 Depreciation and amortization (a) 376 6 25 407 Total operating expenses, net (a) 1,700 252 (21 ) 1,931 Interest, net 249 (2 ) 61 308 Income from continuing operations before income taxes (a) 655 53 (100 ) 608 Provision for income taxes 255 14 (32 ) 237 Income from continuing operations 400 39 (68 ) 371 Total assets (b) 13,448 286 1,330 15,064 Assets of discontinued operations (included in total assets above) — 8 — 8 Capital expenditures 973 7 — 980 Capital expenditures of discontinued operations (included in capital expenditures above) — 1 — 1 (a) The information has been revised to reflect the impact of discontinued operations, as applicable. See Note 3—Acquisitions and Divestitures for additional details on the Company’s discontinued operations. (b) The information has been revised to reflect the retrospective application of ASU 2015-15 Presentation of Debt Issuance Costs and ASU 2015-17 Income Taxes. See Note 2–Significant Accounting Policies for additional details.

Unaudited Quarterly Data (Table

Unaudited Quarterly Data (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Schedule Of Unaudited Quarterly Data	The following table summarizes certain supplemental unaudited consolidated quarterly financial data for each of the four quarters in the years ended December 31, 2015 and 2014, respectively. The operating results for any quarter are not indicative of results that may be expected for a full year or any future periods. 2015 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Operating revenues $ 698 $ 782 $ 896 $ 783 Operating income 204 278 361 232 Net income attributable to common stockholders 80 123 174 99 Basic earnings per share: Net income attributable to common stockholders 0.45 0.69 0.97 0.55 Diluted earnings per share: Net income attributable to common stockholders 0.44 0.68 0.96 0.55 2014 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Operating revenues $ 679 $ 755 $ 846 $ 731 Operating income 187 255 337 224 Net income attributable to common stockholders 68 109 152 94 Basic earnings per share: Net income attributable to common stockholders 0.38 0.61 0.85 0.52 Diluted earnings per share: Net income attributable to common stockholders 0.38 0.61 0.85 0.52

Significant Accounting Polici51

Significant Accounting Policies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)Segment	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Jul. 31, 2015
Significant Accounting Policies [Line Items]
Voting interest	50.00%
Ownership percentage in subsidiary				95.00%
Redeemable noncontrolling interest	$ 7
Minority owners ownership interest	5.00%
Number of non-reportable operating segments for market-based businesses | Segment	4
Estimated refunds	$ 19	$ 18
Amortization of contributions in aid of construction	$ 26	24	$ 22
Agreements range	50 years
Remediation costs accrued	$ 1	2
Accrual for environmental loss contingencies payments	1
Recognized cumulative effect adjustment	8
Other assets decreased due to revision of balance sheet	(7)
Long-term debt decreased due to revision of balance sheet	(7)
Unamortized debt issuance costs included in the long-term debt	7	6
Decrease in current deferred income tax asset	(87)
Decrease in long-term deferred income tax liability	$ (87)
Maximum | Military Services Agreements
Significant Accounting Policies [Line Items]
Agreements range	50 years
Maximum | Operations And Maintenance
Significant Accounting Policies [Line Items]
Agreements range	40 years
Minimum | Operations And Maintenance
Significant Accounting Policies [Line Items]
Agreements range	2 years
Market-Based Businesses
Significant Accounting Policies [Line Items]
Number of non-reportable operating segments for market-based businesses | Segment	4
Software
Significant Accounting Policies [Line Items]
Acquisition cost, carrying value	$ 311	$ 320

Significant Accounting Polici52

Significant Accounting Policies - Schedule of Allowance for Funds Used During Construction (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Funds
Significant Accounting Policies [Line Items]
Allowance for funds used during construction	$ 13	$ 9	$ 13
Borrowed Funds
Significant Accounting Policies [Line Items]
Allowance for funds used during construction	$ 8	$ 6	$ 6

Acquisitions and Divestitures -

Acquisitions and Divestitures - Additional Information (Details)	Nov. 14, 2013USD ($)	Nov. 30, 2014USD ($)	Dec. 31, 2015USD ($)Investment	Dec. 31, 2014USD ($)Investment	Dec. 31, 2013USD ($)Investment	Dec. 12, 2014USD ($)
Business Acquisition And Divestitures [Line Items]
Purchase price allocation, assets acquired, plant					$ 67,000,000
Purchase price allocation, liabilities assumed					43,000,000
Contributions in aid of construction					26,000,000
Debt related to purchase price allocation			$ 1,000,000		13,000,000
Goodwill			1,302,000,000	$ 1,208,000,000
Assets of discontinued operations			0	0	$ 8,000,000
Liabilities of discontinued operations			0	$ 0
Terratec Environmental Limited
Business Acquisition And Divestitures [Line Items]
Proceeds from sale of stock		$ 1,000,000
Gain (loss) on sale of assets included in discontinued operation		$ (1,000,000)
Keystone Clearwater Solutions
Business Acquisition And Divestitures [Line Items]
Purchase price			133,000,000
Purchase price allocation, liabilities assumed			7,000,000
Goodwill			91,000,000
Fair value of assets acquired			56,000,000
Acquisition of nonutility property			25,000,000
Estimated fair value of the redeemable noncontrolling interest			7,000,000
Account receivable and unbilled revenues			18,000,000
Intangible assets			$ 12,000,000
Dale Service Corporation
Business Acquisition And Divestitures [Line Items]
Purchase price	$ 5,000,000
Purchase price allocation, assets acquired, plant	41,000,000
Purchase price allocation, liabilities assumed	36,000,000
Contributions in aid of construction	19,000,000
Debt related to purchase price allocation	13,000,000
Purchase price allocation, cash acquired	$ 7,000,000
Regulated Water And Wastewater Systems
Business Acquisition And Divestitures [Line Items]
Business acquisition, number of companies acquired | Investment			14	13	15
Purchase price			$ 64,000,000	$ 9,000,000	$ 24,000,000
Purchase price allocation, assets acquired, plant			90,000,000			$ 17,000,000
Purchase price allocation, liabilities assumed			26,000,000			8,000,000
Contributions in aid of construction			10,000,000			5,000,000
Debt related to purchase price allocation			1,000,000			$ 2,000,000
Goodwill			3,000,000
Bargain purchase gain recognized			3,000,000
Business combination, purchase gain deferred as regulatory liability			$ 1,000,000

Summary of Discontinued Operati

Summary of Discontinued Operations Presented in Consolidated Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Loss from discontinued operations, net of tax	$ (7)	$ (2)
Terratec Environmental Limited
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenues	13	23
Total operating expenses, net	19	26
Loss from discontinued operations before income taxes	(6)	(3)
Provision (benefit) for income taxes	1	(1)
Loss from discontinued operations, net of tax	$ (7)	$ (2)

Schedule of Major Classes of Pr

Schedule of Major Classes of Property, Plant and Equipment by Category (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Public Utility Property Plant And Equipment [Line Items]
Construction work in progress	$ 404	$ 303
Total utility plant	18,099	16,891
Nonutility property	405	378
Total property, plant and equipment	$ 18,504	17,269
Weighted Average Useful Life	6 years
Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	3 years
Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	50 years
Utility Plant | Land and Other Non-Depreciable Assets
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 141	137
Utility Plant | Sources of Supply
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 705	681
Weighted Average Useful Life	51 years
Utility Plant | Sources of Supply | Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	12 years
Utility Plant | Sources of Supply | Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	127 years
Utility Plant | Treatment and Pumping Facilities
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 3,070	2,969
Weighted Average Useful Life	39 years
Utility Plant | Treatment and Pumping Facilities | Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	3 years
Utility Plant | Treatment and Pumping Facilities | Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	101 years
Utility Plant | Transmission and Distribution Facilities
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 8,516	7,963
Weighted Average Useful Life	83 years
Utility Plant | Transmission and Distribution Facilities | Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	9 years
Utility Plant | Transmission and Distribution Facilities | Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	156 years
Utility Plant | Services, Meters and Fire Hydrants
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 3,250	3,062
Weighted Average Useful Life	35 years
Utility Plant | Services, Meters and Fire Hydrants | Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	8 years
Utility Plant | Services, Meters and Fire Hydrants | Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	93 years
Utility Plant | General Structures and Equipment
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 1,227	1,096
Weighted Average Useful Life	39 years
Utility Plant | General Structures and Equipment | Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	1 year
Utility Plant | General Structures and Equipment | Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	154 years
Utility Plant | Waste Treatment, Pumping and Disposal
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 313	281
Weighted Average Useful Life	46 years
Utility Plant | Waste Treatment, Pumping and Disposal | Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	2 years
Utility Plant | Waste Treatment, Pumping and Disposal | Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	115 years
Utility Plant | Waste Collection
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$ 473	$ 399
Weighted Average Useful Life	56 years
Utility Plant | Waste Collection | Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	5 years
Utility Plant | Waste Collection | Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	109 years

Property, Plant and Equipment -

Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Depreciation expense	$ 405	$ 392	$ 374
Provision for depreciation, percentage of aggregate average depreciable asset	3.13%	3.20%	3.20%

Schedule of Allowances for Unco

Schedule of Allowances for Uncollectible Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts Notes Loans And Financing Receivable Gross Allowance And Net [Abstract]
Balance as of January 1	$ (35)	$ (34)	$ (27)
Amounts charged to expense	(32)	(37)	(27)
Amounts written off	38	43	24
Recoveries of amounts written off	(10)	(7)	(4)
Balance as of December 31	$ (39)	$ (35)	$ (34)

Summary of Composition of Regul

Summary of Composition of Regulatory Assets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Regulatory Asset [Line Items]
Regulatory assets	$ 1,271	$ 1,153
Deferred Pension Expense
Regulatory Asset [Line Items]
Regulatory assets	269	263
Income Taxes Recoverable through Rates
Regulatory Asset [Line Items]
Regulatory assets	236	229
Removal Costs Recoverable through Rates
Regulatory Asset [Line Items]
Regulatory assets	225	163
Deferred Other Postretirement Benefit Expense
Regulatory Asset [Line Items]
Regulatory assets	90	107
San Clemente Dam Project Costs
Regulatory Asset [Line Items]
Regulatory assets	95	72
Regulatory Balancing Accounts
Regulatory Asset [Line Items]
Regulatory assets	88	60
Debt Expense
Regulatory Asset [Line Items]
Regulatory assets	68	71
Purchase Premium Recoverable through Rates
Regulatory Asset [Line Items]
Regulatory assets	60	60
Deferred Tank Painting Costs
Regulatory Asset [Line Items]
Regulatory assets	37	37
Other
Regulatory Asset [Line Items]
Regulatory assets	$ 103	$ 91

Regulatory Assets and Liabili59

Regulatory Assets and Liabilities - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2008	Dec. 31, 2015	Dec. 31, 2014
Removal Costs Recovered through Rates
Regulatory Asset And Liabilities [Line Items]
Amortization expense of regulatory assets	$ 48
Amortization expense of regulatory assets period end date	2048-11
Deferred Pension Expense
Regulatory Asset And Liabilities [Line Items]
Regulatory assets underfunded status		$ 258	$ 248
Deferred Other Postretirement Benefit Expense
Regulatory Asset And Liabilities [Line Items]
Regulatory assets underfunded status		87	107
San Clemente Dam Project Costs
Regulatory Asset And Liabilities [Line Items]
Construction costs to be recovered via surcharge		$ 76
Regulatory assets amortization period		20 years
Surcharges collections		$ 4	5
Additional costs to be recovered from contributions		34
Contributions collections		8	$ 5
San Clemente Dam Project Costs | Pre-construction Costs
Regulatory Asset And Liabilities [Line Items]
Construction costs to be recovered via surcharge		24
San Clemente Dam Project Costs | Interim Dam Safety Measures and Environmental Costs
Regulatory Asset And Liabilities [Line Items]
Construction costs to be recovered via surcharge		3
San Clemente Dam Project Costs | Construction Costs
Regulatory Asset And Liabilities [Line Items]
Construction costs to be recovered via surcharge		$ 49
Deferred Tank Painting Costs | Minimum
Regulatory Asset And Liabilities [Line Items]
Regulatory assets amortization period		5 years
Deferred Tank Painting Costs | Maximum
Regulatory Asset And Liabilities [Line Items]
Regulatory assets amortization period		15 years

Summary of Composition of Reg60

Summary of Composition of Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 402	$ 392
Removal Costs Recovered through Rates
Regulatory Liabilities [Line Items]
Regulatory liabilities	311	301
Pension and Other Postretirement Benefit Balancing Accounts
Regulatory Liabilities [Line Items]
Regulatory liabilities	59	54
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 32	$ 37

Summary of Changes in Goodwill

Summary of Changes in Goodwill Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Cost, beginning balance	$ 3,648
Total Net, beginning balance	1,208
Goodwill from acquisitions	94
Cost, ending balance	3,742
Total Net, ending balance	1,302
Accumulated Impairment	(2,440)	$ (2,440)
Regulated Businesses
Goodwill [Line Items]
Cost, beginning balance	3,412
Goodwill from acquisitions	3
Cost, ending balance	3,415
Accumulated Impairment	(2,332)	(2,332)
Market-Based Businesses
Goodwill [Line Items]
Cost, beginning balance	236
Goodwill from acquisitions	91
Cost, ending balance	327
Accumulated Impairment	$ (108)	$ (108)

Goodwill and Other Intangible62

Goodwill and Other Intangible Assets - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Finite Lived Intangible Assets [Line Items]
Percentage of estimated fair value of reporting unit exceeded its carrying value	3.00%
Goodwill from acquisitions	$ 94
Market-Based Businesses
Finite Lived Intangible Assets [Line Items]
Goodwill from acquisitions	91
Regulated Businesses
Finite Lived Intangible Assets [Line Items]
Goodwill from acquisitions	3
Keystone Clearwater Solutions | Customer Relationships
Finite Lived Intangible Assets [Line Items]
Intangible assets acquired	$ 12
Intangible assets useful life	8 years
Keystone Clearwater Solutions | Market-Based Businesses
Finite Lived Intangible Assets [Line Items]
Goodwill from acquisitions	$ 91
Keystone Clearwater Solutions | Regulated Businesses
Finite Lived Intangible Assets [Line Items]
Goodwill from acquisitions	$ 3

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015	Feb. 28, 2015
Stockholders Equity Note [Line Items]
Shares of common stock repurchased	2.3
Aggregate cost of shares repurchased	$ 126
Maximum
Stockholders Equity Note [Line Items]
Shares available under the program to purchase outstanding common stock		10
DRIP
Stockholders Equity Note [Line Items]
Shares available for grant	4.5

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Loss by Component, Net of Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	$ (82)	$ (35)
Other comprehensive loss (income)	(6)	(47)	$ 81
Accumulated other comprehensive income (loss) Ending balance	(88)	(82)	(35)
Employee Benefit Plan Funded Status
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	(116)	(70)
Other comprehensive loss (income)	(10)	(46)
Accumulated other comprehensive income (loss) Ending balance	(126)	(116)	(70)
Amortization of Prior Service Cost
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	1	1
Accumulated other comprehensive income (loss) Ending balance	1	1	1
Amortization of Actuarial Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	31	31
Other comprehensive loss (income)	5
Accumulated other comprehensive income (loss) Ending balance	36	31	31
Foreign Currency Translation
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	3	3
Other comprehensive loss (income)	(1)
Accumulated other comprehensive income (loss) Ending balance	2	3	$ 3
Loss on Cash Flow Hedge
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	(1)
Other comprehensive loss (income)		(1)
Accumulated other comprehensive income (loss) Ending balance	$ (1)	$ (1)

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, capitalized amount		$ 0	$ 0	$ 0
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years	3 years	3 years
Unrecognized compensation cost		$ 4,000,000
Weighted-average period (in years)		1 year 4 months 24 days
Total grant date fair value of stock awards		$ 12,000,000	$ 11,000,000	$ 9,000,000
Number of grants	93,000	156,000			139,000
Restricted shares granted		The terms of the grants specified that to the extent certain performance goals, comprised of internal measures and, separately, market thresholds were achieved, the RSUs would vest; if performance goals were surpassed, up to 175% of the target awards would be distributed; and if performance goals were not met, the awards would be forfeited.
Expected term		3 years
Accrued dividend equivalents		$ 1,000,000	$ 1,000,000	$ 1,000,000
Restricted Stock Units | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		1 year
Restricted Stock Units | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years
2007 Omnibus Equity Compensation Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares authorized for grant		15,500,000
Shares available for grant		8,400,000
2007 Omnibus Equity Compensation Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years	3 years	3 years
Maximum terms		7 years
Unrecognized compensation cost		$ 2,000,000
Weighted-average period (in years)		1 year 7 months 6 days
Total grant date fair value of stock awards		$ 3,000,000	$ 3,000,000	$ 4,000,000
2007 Omnibus Equity Compensation Plan | Stock Options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		1 year
2007 Omnibus Equity Compensation Plan | Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grant		1,200,000
Lesser of fair market value		90.00%
Shares issued		98,000	102,000	111,000

Stock-Based Compensation Expens

Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 11	$ 13	$ 13
Income tax benefit	(4)	(5)	(5)
Stock-based compensation expense, net of tax	7	8	8
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	2	2	3
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	8	10	9
Income tax benefit	(2)	(2)	(2)
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 1	$ 1	$ 1

Summary of Weighted-Average Ass

Summary of Weighted-Average Assumptions (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield	2.35%	2.55%	2.52%
Expected volatility	17.64%	17.75%	23.50%
Risk-free interest rate	1.48%	1.06%	0.70%
Expected life (years)	4 years 4 months 24 days	3 years 7 months 6 days	4 years 3 months 18 days
Exercise price	$ 52.75	$ 44.29	$ 39.60
Grant date fair value per share	$ 6.21	$ 4.57	$ 5.78

Summary of Stock Option Activit

Summary of Stock Option Activity (Details) - Stock Options $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding as January 1, 2015 | shares	1,910
Granted | shares	301
Forfeited or expired | shares	(51)
Exercised | shares	(973)
Options outstanding as of December 31, 2015 | shares	1,187
Exercisable as of December 31, 2015 | shares	666
Weighted Average Exercise Price (per share), Options outstanding at January 1, 2015 | $ / shares	$ 33.47
Weighted Average Exercise Price (per share), Granted | $ / shares	52.75
Weighted Average Exercise Price (per share), Forfeited or expired | $ / shares	44.36
Weighted Average Exercise Price (per share), Exercised | $ / shares	31.26
Weighted Average Exercise Price (per share), Options outstanding at December 31, 2015 | $ / shares	39.70
Weighted Average Exercise Price (per share), Options outstanding at December 31, 2015 | $ / shares	$ 32.92
Weighted Average Remaining Life (years), Options outstanding at January 1, 2015	3 years 10 months 24 days
Weighted Average Remaining Life (years), Exercisable at December 31, 2015	2 years 7 months 6 days
Aggregate intrinsic Value, Options outstanding at January 1, 2015 | $	$ 38
Aggregate intrinsic Value, Options outstanding at December 31, 2015 | $	24
Aggregate intrinsic Value, Exercisable at December 31, 2015 | $	$ 18

Additional Information to Stock

Additional Information to Stock Options Exercised (Details) - Stock Options - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value	$ 22	$ 13	$ 15
Exercise proceeds	30	15	20
Income tax benefit	$ 7	$ 4	$ 4

Weighted-Average Assumptions Us

Weighted-Average Assumptions Used in Monte Carlo Simulation (Details) - Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	14.93%	17.78%	19.37%
Risk-free interest rate	1.07%	0.75%	0.40%
Expected life (years)	3 years	3 years	3 years
Grant date fair value per share	$ 62.10	$ 45.45	$ 40.13

Summary of Restricted Stock Uni

Summary of Restricted Stock Unit Activity (Details) - Restricted Stock Units - $ / shares shares in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested total as of January 1, 2015	516	516
Granted	93	156	139
Performance share adjustment		93
Vested		(304)
Forfeited		(25)
Non-vested total as of December 31, 2015		436
Weighted-average grant date fair value (per share), non-vested total beginning balance	$ 41.46	$ 41.46
Weighted-average grant date fair value (per share), granted		55.67
Weighted-average grant date fair value (per share), Performance share adjustment		38.11
Weighted-average grant date fair value (per share), vested		39.46
Weighted-average grant date fair value (per share), forfeited		45.84
Weighted-average grant date fair value (per share), non-vested total ending balance		$ 46.97

Additional Information to Sto72

Additional Information to Stock Options Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Income tax benefit	$ 4	$ 5	$ 5
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value	17	16	14
Income tax benefit	$ 2	$ 2	$ 2

Components of Long-Term Debt (D

Components of Long-Term Debt (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt		$ 5,909	$ 5,474
Unamortized debt premium, net	[1]	23	31
Unamortized debt issuance costs		(7)	(6)
Interest rate swap fair value adjustment		3	4
Total long-term debt		$ 5,928	5,503
Senior notes | American Water Capital Corp. | Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum		3.40%
Interest Rate, Maximum		4.30%
Senior notes | American Water Capital Corp. | Fixed rate | Long Term Debt
Debt Instrument [Line Items]
Interest Rate, Minimum	[2]	3.40%
Interest Rate, Maximum	[2]	8.27%
Weighted Average Rate	[2]	5.23%
Maturity Date, Minimum	[2]	2,016
Maturity Date, Maximum	[2]	2,045
Long-term debt	[2]	$ 4,273	3,753
Private activity bonds and government funded debt | American Water Capital Corp. | Fixed rate | Long Term Debt
Debt Instrument [Line Items]
Interest Rate, Minimum	[2]	1.79%
Interest Rate, Maximum	[2]	6.25%
Weighted Average Rate	[2]	5.41%
Maturity Date, Minimum	[2]	2,021
Maturity Date, Maximum	[2]	2,040
Long-term debt	[2]	$ 195	231
Private activity bonds and government funded debt | Other American Water subsidiaries | Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum		0.00%
Interest Rate, Maximum		5.00%
Private activity bonds and government funded debt | Other American Water subsidiaries | Fixed rate | Long Term Debt
Debt Instrument [Line Items]
Interest Rate, Minimum	[3]	0.00%
Interest Rate, Maximum	[3]	6.20%
Weighted Average Rate	[3]	4.70%
Maturity Date, Minimum	[3]	2,016
Maturity Date, Maximum	[3]	2,041
Long-term debt	[3]	$ 790	795
Mortgage bonds | Other American Water subsidiaries | Fixed rate | Long Term Debt
Debt Instrument [Line Items]
Interest Rate, Minimum		4.29%
Interest Rate, Maximum		9.71%
Weighted Average Rate		7.41%
Maturity Date, Minimum		2,017
Maturity Date, Maximum		2,039
Long-term debt		$ 637	677
Capital lease obligations | Other American Water subsidiaries | Long Term Debt
Debt Instrument [Line Items]
Interest Rate, Minimum		12.23%
Weighted Average Rate		12.23%
Maturity Date, Maximum		2,026
Long-term debt		$ 1	1
Mandatorily redeemable preferred stock | Other American Water subsidiaries | Long Term Debt
Debt Instrument [Line Items]
Interest Rate, Minimum		8.47%
Interest Rate, Maximum		9.75%
Weighted Average Rate		8.61%
Maturity Date, Minimum		2,019
Maturity Date, Maximum		2,036
Long-term debt		$ 13	$ 17
[1]	Primarily fair value adjustments previously recognized in acquisition purchase accounting
[2]	This indebtedness is considered “debt” for purposes of a support agreement between American Water and American Water Capital Corp. (“AWCC”), which serves as a functional equivalent of a guarantee by AWCC’s payment obligations under such indebtedness.
[3]	Includes $8 and $10 of variable rate debt with variable-to-fixed interest rate swaps ranging between 4.65% and 3.93%, as of December 31, 2015 and 2014, respectively. This debt was assumed via an acquisition in 2013

Components of Long-Term Debt (P

Components of Long-Term Debt (Parenthetical) (Details) - Interest Rate Swap - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Variable rate debt	$ 8	$ 10
Minimum
Debt Instrument [Line Items]
Variable-to-fixed rate	4.65%
Maximum
Debt Instrument [Line Items]
Variable-to-fixed rate		3.93%

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details)	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 5,909,000,000	$ 5,474,000,000
Line of credit facility consolidated debt to consolidated capitalization ratio	0.56
Redeemable debt, amount outstanding	$ 985,000,000
Business acquisition, assumed debt	1,000,000		$ 13,000,000
Debt issuance cost	$ 5,000,000
Interest Rate	1.00%
Maturity Date	2,040
Interest income	$ 13,000,000	$ 11,000,000	$ 12,000,000
Interest Rate Swap
Debt Instrument [Line Items]
Interest Rate	6.085%
Fixed rate debt	$ 100,000,000
Derivative description of variable rate basis	six-month LIBOR plus 3.422
Maturity Date, Maximum	2,017
Interest Rate Swap | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, basis spread on variable rate	3.422%
Line of Credit
Debt Instrument [Line Items]
Line of credit facility consolidated debt to consolidated capitalization ratio	0.70
6.085% Senior Notes
Debt Instrument [Line Items]
Maturity Date, Maximum	2,017
Other American Water subsidiaries | Private activity bonds and government funded debt | Collateralized Debt Obligations
Debt Instrument [Line Items]
Long-term debt	$ 716,000,000

Future Sinking Fund Payments an

Future Sinking Fund Payments and Maturities (Details) $ in Millions	Dec. 31, 2015USD ($)
Debt Disclosure [Abstract]
2,016	$ 54
2,017	573
2,018	457
2,019	166
2,020	22
Thereafter	$ 4,637

Long-Term Debt Issued (Details)

Long-Term Debt Issued (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Maturity Date	2,040
Total issuances	$ 565
AWCC | Senior notes | Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	3.40%
Interest Rate, Maximum	4.30%
Total issuances	$ 550
AWCC | Senior notes | Minimum | Fixed rate
Debt Instrument [Line Items]
Maturity Date	2,025
AWCC | Senior notes | Maximum | Fixed rate
Debt Instrument [Line Items]
Maturity Date	2,045
Other American Water subsidiaries | Private activity bonds and government funded debt | Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	0.00%
Interest Rate, Maximum	5.00%
Maturity Date	2,032
Total issuances	$ 15

Long-Term Debt Retired through

Long-Term Debt Retired through Sinking Fund Payments and Maturities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Interest Rate	1.00%
Debt retired during the year
Debt Instrument [Line Items]
Total retirements and redemptions	$ 131
Debt retired during the year | Other American Water subsidiaries | Mandatorily redeemable preferred stock
Debt Instrument [Line Items]
Interest Rate, Minimum	8.49%
Interest Rate, Maximum	9.18%
Maturity Date, Minimum	2,031
Maturity Date, Maximum	2,036
Total retirements and redemptions	$ 4
Debt retired during the year | Fixed rate two | AWCC | Private activity bonds and government funded debt
Debt Instrument [Line Items]
Interest Rate, Minimum	1.79%
Interest Rate, Maximum	5.25%
Maturity Date, Minimum	2,015
Maturity Date, Maximum	2,031
Total retirements and redemptions	$ 36
Debt retired during the year | Fixed rate two | AWCC | Senior notes
Debt Instrument [Line Items]
Interest Rate	6.00%
Maturity Date, Maximum	2,015
Total retirements and redemptions	$ 30
Debt retired during the year | Fixed rate two | Other American Water subsidiaries | Private activity bonds and government funded debt
Debt Instrument [Line Items]
Interest Rate, Minimum	0.00%	[1]
Interest Rate, Maximum	5.40%	[1]
Maturity Date, Minimum	2,015	[1]
Maturity Date, Maximum	2,041	[1]
Total retirements and redemptions	$ 61	[1]
[1]	Includes $2 of non-cash defeasance via the use of restricted funds.

Long-Term Debt Retired throug79

Long-Term Debt Retired through Sinking Fund Payments and Maturities (Parenthetical) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Debt Disclosure [Abstract]
Non-cash defeasance	$ 2

Summary of Derivative Fair Valu

Summary of Derivative Fair Value Balance (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Regulatory and other long-term assets	$ 2	$ 4
Interest rate swap fair value adjustment	3	4
Interest Rate Swap
Derivative [Line Items]
Interest rate swap fair value adjustment	2	4
Other
Derivative [Line Items]
Regulatory and other long-term assets	$ 2	$ 4

Derivative and Hedged Item (Det

Derivative and Hedged Item (Details) - Interest, net - Designated as Hedging Instrument - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments Gain Loss [Line Items]
Loss on swap	$ (1)	$ (1)	$ (3)
Gain on borrowing	$ 1	$ 1	$ 3

Short-Term Debt - Additional In

Short-Term Debt - Additional Information (Details)		1 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Short Term Debt [Line Items]
Short-term debt			$ 628,000,000	$ 450,000,000
Proceeds from short-term borrowings with maturities greater than three months			60,000,000	35,000,000	$ 221,000,000
Debt issuance costs			$ 7,000,000	5,000,000	$ 4,000,000
Line of credit facility consolidated debt to consolidated capitalization ratio			0.56
Line of credit facility consolidated debt to consolidated capitalization ratio			0.70
American Water Capital Corp.
Short Term Debt [Line Items]
Line of credit facility term extension description			The amended and restated agreement also allows AWCC to request to further extend the term of the credit facility for up to two one-year periods.
Maturity in More Than Three Months
Short Term Debt [Line Items]
Proceeds from short-term borrowings with maturities greater than three months			$ 0
Commercial Paper Program
Short Term Debt [Line Items]
Short-term debt			628,000,000	450,000,000
Revolving Credit Facility
Short Term Debt [Line Items]
Maximum borrowing capacity			1,266,000,000	1,250,000,000
Available credit facility capacity			1,182,000,000	1,212,000,000
Revolving Credit Facility | Keystone Clearwater Solutions
Short Term Debt [Line Items]
Maximum borrowing capacity			16,000,000
Available credit facility capacity			$ 14,000,000
Derivative description of variable rate basis			one month or one day LIBOR
Revolving Credit Facility | Keystone Clearwater Solutions | London Interbank Offered Rate (LIBOR) [Member]
Short Term Debt [Line Items]
Debt, basis spread on variable rate			2.75%
Revolving Credit Facility | American Water Capital Corp.
Short Term Debt [Line Items]
Maximum borrowing capacity			$ 1,250,000,000
Line of credit facility, swing loan sublimit			100,000,000
Debt issuance costs			2,000,000
Revolving Credit Facility | Letter of Credit
Short Term Debt [Line Items]
Maximum borrowing capacity	[1]		150,000,000	150,000,000
Available credit facility capacity			68,000,000	$ 112,000,000
Revolving Credit Facility | Letter of Credit | American Water Capital Corp.
Short Term Debt [Line Items]
Maximum borrowing capacity			$ 150,000,000
Credit Facility June Two Thousand Twenty | American Water Capital Corp.
Short Term Debt [Line Items]
New agreement expiration date		2018-10
New agreement extended expiration date		2020-06
[1]	Letters of credit are non-debt instruments maintained to provide credit support for certain transactions as requested by third parties. The Company had $82 and $38 of outstanding letters of credit as of December 31, 2015 and 2014, respectively, all of which were issued under the revolving credit facility noted above.

Schedule of Company's Aggregate

Schedule of Company's Aggregate Credit Facility Commitments, Letter of Credit Sub-Limit Under Revolving Credit Facility and Commercial Paper Limit and Available Capacity (Details) - USD ($)		Dec. 31, 2015	Dec. 31, 2014
Revolving Credit Facility
Short Term Debt [Line Items]
Credit Facility Commitment		$ 1,266,000,000	$ 1,250,000,000
Available Credit Facility Capacity		1,182,000,000	1,212,000,000
Letter of Credit Sublimit		1,266,000,000	1,250,000,000
Commercial Paper Program
Short Term Debt [Line Items]
Commercial Paper Limit		1,000,000,000	1,000,000,000
Available Commercial Paper Capacity		374,000,000	550,000,000
Letter of Credit | Revolving Credit Facility
Short Term Debt [Line Items]
Credit Facility Commitment	[1]	150,000,000	150,000,000
Available Credit Facility Capacity		68,000,000	112,000,000
Letter of Credit Sublimit	[1]	$ 150,000,000	$ 150,000,000
[1]	Letters of credit are non-debt instruments maintained to provide credit support for certain transactions as requested by third parties. The Company had $82 and $38 of outstanding letters of credit as of December 31, 2015 and 2014, respectively, all of which were issued under the revolving credit facility noted above.

Schedule of Company's Aggrega84

Schedule of Company's Aggregate Credit Facility Commitments, Letter of Credit Sub-Limit Under Revolving Credit Facility and Commercial Paper Limit and Available Capacity (Parenthetical) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Revolving Credit Facility
Short Term Debt [Line Items]
Letters of credit, outstanding amount	$ 82	$ 38

Schedule of Short-Term Borrowin

Schedule of Short-Term Borrowings Activity (Details) - American Water Capital Corp. - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Short Term Debt [Line Items]
Average borrowings	$ 553	$ 549
Maximum borrowings outstanding	$ 871	$ 745
Weighted average interest rates, computed on daily basis	0.49%	0.31%
Weighted average interest rates, ending balance	0.66%	0.42%

Components of General Tax Expen

Components of General Tax Expense from Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
General Tax Expense [Line Items]
Gross receipts and franchise	$ 99	$ 96	$ 96
Property and capital stock	98	96	94
Payroll	31	31	31
Total general taxes	243	236	234
Other general
General Tax Expense [Line Items]
General taxes	$ 15	$ 13	$ 13

Components of Income Tax Expens

Components of Income Tax Expense from Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
State	$ 10	$ 11	$ 7
Federal		15	(20)
Total current income taxes	10	26	(13)
State	32	31	27
Federal	265	224	225
Amortization of deferred investment tax credits	(1)	(1)	(2)
Total deferred income taxes	296	254	250
Provision for income taxes	$ 306	$ 280	$ 237

Reconciliation of Income Tax Ex

Reconciliation of Income Tax Expense from Continuing Operations (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax at statutory rate	35.00%	35.00%	35.00%
State taxes, net of federal taxes	3.60%	3.80%	3.60%
Flow through differences	0.50%	0.40%	0.50%
Amortization of deferred investment tax credits	(0.10%)	(0.10%)	(0.30%)
Subsidiary preferred dividends		0.10%	0.20%
Other, net	0.10%	0.20%
Provision for income taxes	39.10%	39.40%	39.00%

Components of Net Deferred Tax

Components of Net Deferred Tax Liability from Continuing Operations (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Advances and contributions	$ 513	$ 502
Other postretirement benefits	76	105
Tax losses and credits	173	197
Pension benefits	105	125
Unamortized debt discount, net	20	20
Other	12	42
Total deferred tax assets	899	991
Valuation allowance	(8)	(10)	$ (13)	$ (19)
Total deferred tax assets, net of allowance	891	981
Property, plant and equipment, principally due to depreciation differences	2,913	2,677
Income taxes recoverable through rates	76	76
Deferred other postretirement benefits	35	65
Deferred pension benefits	104	121
Other	73	76
Total deferred tax liabilities	3,201	3,015
Total deferred tax liabilities, net of deferred tax assets	$ (2,310)	$ (2,034)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Income Tax Examination [Line Items]
Capital loss carry forwards	$ 4		$ 4
Net of deferred tax assets and regulatory assets	6		6
Deferred tax liabilities	2,310		2,034
Unrecognized tax benefit excluding interest and penalties, that would affect the effective tax rate	9		9
Regulated Businesses
Income Tax Examination [Line Items]
Deferred tax liabilities		$ 89
Federal
Income Tax Examination [Line Items]
Net operating loss carryforwards	1,080		1,005
Tax benefits on stock-based compensation	$ 37
Net operating loss carryforwards expiration date	The Company’s federal NOL carryforwards will begin to expire in 2028
State
Income Tax Examination [Line Items]
Net operating loss carryforwards	$ 534		543
Net operating loss carryforwards expiration date	The state NOL carryforwards will begin to expire in 2016 through 2034
Canadian
Income Tax Examination [Line Items]
Net operating loss carryforwards	$ 2		$ 6
Net operating loss carryforwards expiration date	The Canadian NOL carryforwards will expire between 2026 through 2034

Changes in Gross Liability Excl

Changes in Gross Liability Excluding Interest and Penalties for Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Beginning Balance	$ 195	$ 178
Increases in current period tax positions	39	54
Decreases in prior period measurement of tax positions	(1)	(37)
Ending Balance	$ 233	$ 195

Changes in Valuation Allowance

Changes in Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation Allowance [Line Items]
Beginning Balance	$ 10	$ 13	$ 19
Ending Balance	8	10	13
Decrease
Valuation Allowance [Line Items]
Current period tax positions	$ (2)	$ (3)	$ (6)

Employee Benefits - Additional

Employee Benefits - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Base pay rate of contribution plan		5.25%
Percentage return expected from plan assets	60.00%
Percentage of liability driven assets	40.00%
Minimum reduction of expected future service of plan participants		10.00%
Cumulative gains losses as percentage of benefit obligations or plan assets		10.00%
Cost of contribution plan		$ 9	$ 8	$ 8
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Benefits paid		61	112
Expected employer contributions, 2016		$ 9
Expected return on plan assets percentage		7.02%
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Benefits paid		$ 26	26
Expected employer contributions, 2016		$ 6
Expected return on plan assets percentage		5.20%
One-time Termination Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefits paid			$ 56

Schedule of Changes in Fair Val

Schedule of Changes in Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%	100.00%
Fair value of plan assets	$ 1,376	$ 1,428	$ 1,384
Percentage of Plan Assets	100.00%	100.00%
Pension Plan Asset | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 540	$ 595
Pension Plan Asset | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	700	706
Pension Plan Asset | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 136	$ 127
Pension Plan Asset | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	6.00%	6.00%
Fair value of plan assets	$ 95	$ 85
Percentage of Plan Assets	7.00%	6.00%
Pension Plan Asset | Real Estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 95	$ 85
Pension Plan Asset | REITs
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	2.00%	2.00%
Fair value of plan assets	$ 23	$ 23
Percentage of Plan Assets	2.00%	2.00%
Pension Plan Asset | REITs | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 23	$ 23
Pension Plan Asset | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	8
Pension Plan Asset | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 5	$ 8
Pension Plan Asset | Equity Securities | U.S. large cap
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	24.00%	24.00%
Fair value of plan assets	$ 318	$ 342
Percentage of Plan Assets	23.00%	24.00%
Pension Plan Asset | Equity Securities | U.S. large cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 318	$ 342
Pension Plan Asset | Equity Securities | U.S. small cap
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	8.00%	8.00%
Fair value of plan assets	$ 115	$ 117
Percentage of Plan Assets	8.00%	8.00%
Pension Plan Asset | Equity Securities | U.S. small cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 115	$ 117
Pension Plan Asset | Equity Securities | International
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	20.00%	20.00%
Fair value of plan assets	$ 260	$ 274
Percentage of Plan Assets	19.00%	19.00%
Pension Plan Asset | Equity Securities | International | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 260	$ 274
Pension Plan Asset | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	40.00%	40.00%
Percentage of Plan Assets	41.00%	41.00%
Pension Plan Asset | Fixed Income Securities | U.S. Treasury and government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 120	$ 140
Pension Plan Asset | Fixed Income Securities | U.S. Treasury and government bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	95	121
Pension Plan Asset | Fixed Income Securities | U.S. Treasury and government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25	19
Pension Plan Asset | Fixed Income Securities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	375	377
Pension Plan Asset | Fixed Income Securities | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	375	377
Pension Plan Asset | Fixed Income Securities | Mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	4
Pension Plan Asset | Fixed Income Securities | Mortgage-backed securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	4
Pension Plan Asset | Fixed Income Securities | Long duration bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	7
Pension Plan Asset | Fixed Income Securities | Long duration bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	7
Pension Plan Asset | Fixed Income Securities | Guarantee annuity contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49	51
Pension Plan Asset | Fixed Income Securities | Guarantee annuity contracts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	9
Pension Plan Asset | Fixed Income Securities | Guarantee annuity contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 41	$ 42
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%	100.00%
Fair value of plan assets	$ 500	$ 512	$ 475
Percentage of Plan Assets	100.00%	100.00%
Postretirement Benefit Plan Assets | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%	100.00%
Fair value of plan assets	$ 376	$ 402
Percentage of Plan Assets	100.00%	100.00%
Postretirement Benefit Plan Assets | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%	100.00%
Fair value of plan assets	$ 118	$ 103
Percentage of Plan Assets	100.00%	100.00%
Postretirement Benefit Plan Assets | Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%	100.00%
Fair value of plan assets	$ 6	$ 7
Percentage of Plan Assets	100.00%	100.00%
Postretirement Benefit Plan Assets | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 316	$ 344
Postretirement Benefit Plan Assets | Level 1 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	192	234
Postretirement Benefit Plan Assets | Level 1 | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	118	103
Postretirement Benefit Plan Assets | Level 1 | Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	7
Postretirement Benefit Plan Assets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	184	168
Postretirement Benefit Plan Assets | Level 2 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	184	168
Postretirement Benefit Plan Assets | Cash | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	1
Postretirement Benefit Plan Assets | Cash | Level 1 | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2	$ 1
Postretirement Benefit Plan Assets | Equity Securities | U.S. large cap | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	9.00%	9.00%
Fair value of plan assets	$ 32	$ 34
Percentage of Plan Assets	9.00%	9.00%
Postretirement Benefit Plan Assets | Equity Securities | U.S. large cap | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	21.00%	21.00%
Fair value of plan assets	$ 24	$ 22
Percentage of Plan Assets	21.00%	21.00%
Postretirement Benefit Plan Assets | Equity Securities | U.S. large cap | Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	70.00%	70.00%
Fair value of plan assets	$ 4	$ 5
Percentage of Plan Assets	68.00%	67.00%
Postretirement Benefit Plan Assets | Equity Securities | U.S. large cap | Level 1 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 32	$ 34
Postretirement Benefit Plan Assets | Equity Securities | U.S. large cap | Level 1 | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24	22
Postretirement Benefit Plan Assets | Equity Securities | U.S. large cap | Level 1 | Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 4	$ 5
Postretirement Benefit Plan Assets | Equity Securities | U.S. small cap | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	21.00%	21.00%
Fair value of plan assets	$ 26	$ 21
Percentage of Plan Assets	22.00%	21.00%
Postretirement Benefit Plan Assets | Equity Securities | U.S. small cap | Level 1 | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 26	$ 21
Postretirement Benefit Plan Assets | Equity Securities | International | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	11.00%	11.00%
Fair value of plan assets	$ 38	$ 41
Percentage of Plan Assets	10.00%	10.00%
Postretirement Benefit Plan Assets | Equity Securities | International | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	28.00%	28.00%
Fair value of plan assets	$ 33	$ 28
Percentage of Plan Assets	28.00%	28.00%
Postretirement Benefit Plan Assets | Equity Securities | International | Level 1 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 38	$ 41
Postretirement Benefit Plan Assets | Equity Securities | International | Level 1 | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 33	$ 28
Postretirement Benefit Plan Assets | Fixed Income Securities | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	80.00%	80.00%
Percentage of Plan Assets	81.00%	81.00%
Postretirement Benefit Plan Assets | Fixed Income Securities | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	30.00%	30.00%
Percentage of Plan Assets	29.00%	30.00%
Postretirement Benefit Plan Assets | Fixed Income Securities | Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	30.00%	30.00%
Percentage of Plan Assets	32.00%	33.00%
Postretirement Benefit Plan Assets | Fixed Income Securities | U.S. Treasury and government bonds | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 118	$ 155
Postretirement Benefit Plan Assets | Fixed Income Securities | U.S. Treasury and government bonds | Level 1 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	118	155
Postretirement Benefit Plan Assets | Fixed Income Securities | Corporate bonds | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	184	168
Postretirement Benefit Plan Assets | Fixed Income Securities | Corporate bonds | Level 2 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	184	168
Postretirement Benefit Plan Assets | Fixed Income Securities | Long duration bonds | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	3
Postretirement Benefit Plan Assets | Fixed Income Securities | Long duration bonds | Level 1 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	3
Postretirement Benefit Plan Assets | Fixed Income Securities | Future and option contracts | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Postretirement Benefit Plan Assets | Fixed Income Securities | Future and option contracts | Level 1 | Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Postretirement Benefit Plan Assets | Fixed Income Securities | Core fixed income bond fund | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33	31
Postretirement Benefit Plan Assets | Fixed Income Securities | Core fixed income bond fund | Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	2
Postretirement Benefit Plan Assets | Fixed Income Securities | Core fixed income bond fund | Level 1 | Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33	31
Postretirement Benefit Plan Assets | Fixed Income Securities | Core fixed income bond fund | Level 1 | Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2	$ 2

Schedule of Significant Unobser

Schedule of Significant Unobservable Inputs (Details) - Pension Plan Asset - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	$ 1,428	$ 1,384
Actual return on assets	(21)	116
Fair value of plan assets ending balance	1,376	1,428
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	127
Purchases, issuances and settlements, net	(3)	76
Fair value of plan assets ending balance	136	127
Level 3 | Guaranteed Annuity Contracts And Real Estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	127	44
Actual return on assets	12	7
Fair value of plan assets ending balance	$ 136	$ 127

Schedule of Rollforward Changes

Schedule of Rollforward Changes in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Noncurrent liability	$ (342)	$ (316)
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation beginning balance	1,746	1,494
Service cost	37	32	$ 37
Interest cost	74	76	68
Actuarial (gain) loss	(76)	256
Benefits paid	(61)	(112)
Benefit obligation ending balance	1,720	1,746	1,494
Fair value of plan assets beginning balance	1,428	1,384
Actual return on assets	(21)	116
Employer contributions	30	40
Fair value of plan assets ending balance	1,376	1,428	1,384
Funded status ending balance	(344)	(318)
Current liability	(2)	(2)
Noncurrent liability	(342)	(316)
Net amount recognized	(344)	(318)
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation beginning balance	703	562
Service cost	14	11	15
Interest cost	30	29	29
Plan participants' contributions	2	2
Actuarial (gain) loss	(58)	123
Benefits paid	(26)	(26)
Federal subsidy	2	2
Benefit obligation ending balance	667	703	562
Fair value of plan assets beginning balance	512	475
Actual return on assets	(15)	49
Employer contributions	27	12
Fair value of plan assets ending balance	500	512	$ 475
Funded status ending balance	(167)	(191)
Noncurrent asset	2	1
Noncurrent liability	(169)	(192)
Net amount recognized	$ (167)	$ (191)

Summary of Accumulated Other Co

Summary of Accumulated Other Comprehensive Income and Regulatory Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 397	$ 379
Prior service cost (credit)	3	4
Net amount recognized	400	383
Regulatory assets	258	248
Accumulated other comprehensive income	142	135
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	97	119
Prior service cost (credit)	(10)	(12)
Net amount recognized	87	107
Regulatory assets	$ 87	$ 107

Schedule of Accumulated and Pro

Schedule of Accumulated and Projected Benefit Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Projected benefit obligation	$ 1,721	$ 1,746
Projected benefit obligation exceeds, fair value of plan assets	1,376	1,428
Accumulated benefit obligation	1,584	1,616
Accumulated benefit obligation exceeds, fair value of plan assets	$ 1,376	$ 1,428

Schedule of Expected Cash Flow

Schedule of Expected Cash Flow for Pension and Post Retirement Benefit Plans (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2016	$ 9
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2016	6
To Plan Trusts | Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2016	33
To Plan Trusts | Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2016	22
To Plan Participants | Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2016	$ 2

Schedule of Expected Benefit Pa

Schedule of Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2015USD ($)
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
2,016	$ 65
2,017	70
2,018	76
2,019	82
2,020	89
2021-2025	525
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
2,016	28
2,017	30
2,018	32
2,019	35
2,020	37
2021-2025	212
Expected Federal Subsidy Payments | Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
2,016	2
2,017	2
2,018	2
2,019	3
2,020	3
2021-2025	$ 18

Schedule of Pension and Post Re

Schedule of Pension and Post Retirement Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Benefit Obligations | Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations, Discount rate	4.66%	4.24%	5.12%
Weighted average assumptions used to determine benefit obligations, Rate of compensation increase	3.10%	3.12%	3.15%
Benefit Obligations | Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations, Discount rate	4.67%	4.24%	5.10%
Benefit Obligations | Postretirement Benefit Plan Assets | Maximum
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations and net periodic cost, Medical trend rate	6.50%	6.75%	7.00%
Benefit Obligations | Postretirement Benefit Plan Assets | Minimum
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations and net periodic cost, Medical trend rate	5.00%	5.00%	5.00%
Weighted average assumptions used to determine benefit obligations and net periodic cost, Year reaches Medical trend rate	2,021	2,021	2,019
Net Periodic Costs | Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine net periodic cost, Discount rate	4.24%	5.12%	4.17%
Weighted average assumptions used to determine net periodic cost, Expected return on plan assets	6.91%	6.91%	7.49%
Weighted average assumptions used to determine net periodic cost, Rate of compensation increase	3.12%	3.15%	3.19%
Net Periodic Costs | Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine net periodic cost, Discount rate	4.24%	5.10%	4.16%
Weighted average assumptions used to determine net periodic cost, Expected return on plan assets	4.92%	5.87%	6.99%
Net Periodic Costs | Postretirement Benefit Plan Assets | Maximum
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations and net periodic cost, Medical trend rate	6.75%	7.00%	7.25%
Net Periodic Costs | Postretirement Benefit Plan Assets | Minimum
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations and net periodic cost, Medical trend rate	5.00%	5.00%	5.00%
Weighted average assumptions used to determine benefit obligations and net periodic cost, Year reaches Medical trend rate	2,021	2,019	2,019

Schedule of Effect of One Perce

Schedule of Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Compensation And Retirement Disclosure [Abstract]
Effect on total of service and interest cost components, One - Percentage - Point Increase	$ 8
Effect on other postretirement benefit obligation, One - Percentage - Point Increase	99
Effect on total of service and interest cost components, One - Percentage - Point Decrease	(6)
Effect on other postretirement benefit obligation One - Percentage - Point Decrease	$ (81)

Schedule of Net Periodic Benefi

Schedule of Net Periodic Benefit Cost Components (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial (gain) loss	$ 10	$ 46	$ (73)
Amortization of actuarial gain (loss)	(5)		(9)
Total recognized in other comprehensive income	5	46	(82)
Total recognized in net periodic benefit cost and comprehensive income	45	60	(27)
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Service cost	37	32	37
Interest cost	74	76	68
Expected return on plan assets	(97)	(95)	(88)
Prior service cost (credit)	1	1	1
Actuarial (gain) loss	25		37
Net periodic pension benefit cost	40	14	55
Other Postretirement Benefit Cost
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	11	15
Interest cost	30	29	29
Expected return on plan assets	(26)	(28)	(30)
Prior service cost (credit)	(2)	(2)	(2)
Actuarial (gain) loss	5		11
Net periodic pension benefit cost	$ 21	$ 10	$ 23

Schedule of Estimated Amounts A

Schedule of Estimated Amounts Amortized Accumulated Other Comprehensive Income (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$ 27
Prior service cost (credit)	1
Net amount recognized	28
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	3
Prior service cost (credit)	(2)
Net amount recognized	$ 1

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)CustomerAccount
Loss Contingencies [Line Items]
Estimated capital expenditures under legal and binding contractual obligations	$ 238
Loss contingency, probable loss	5
Loss contingency, range of reasonably possible loss, maximum	$ 36
Number of customer accounts | CustomerAccount	93,000
Military Services Agreements
Loss Contingencies [Line Items]
Estimated remaining contract revenue	$ 2,784
Military Services Agreements | Minimum
Loss Contingencies [Line Items]
Agreements expiration period	2,051
Military Services Agreements | Maximum
Loss Contingencies [Line Items]
Agreements expiration period	2,065
Operations And Maintenance
Loss Contingencies [Line Items]
Estimated remaining contract revenue	$ 795
Operations And Maintenance | Minimum
Loss Contingencies [Line Items]
Agreements expiration period	2,016
Operations And Maintenance | Maximum
Loss Contingencies [Line Items]
Agreements expiration period	2,048

Commitments and Contingencie106

Commitments and Contingencies - Summary of Future Annual Commitments Related to Minimum Quantities of Purchased Water Having Non-Cancelable Terms (Details) $ in Millions	Dec. 31, 2015USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,016	$ 51
2,017	45
2,018	44
2,019	43
2,020	44
Thereafter	$ 383

Reconciliation of Numerator and

Reconciliation of Numerator and Denominator for Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Income from continuing operations									$ 476	$ 430	$ 371
Loss from discontinued operations, net of tax										(7)	(2)
Net income attributable to common stockholders	$ 99	$ 174	$ 123	$ 80	$ 94	$ 152	$ 109	$ 68	$ 476	$ 423	$ 369
Weighted average common shares outstanding—Basic									179	179	178
Effect of dilutive common stock equivalents									1	1	1
Weighted average common shares outstanding—Diluted									180	180	179

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Maximum
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	1	1	1

Carrying Amounts and Fair Value

Carrying Amounts and Fair Values of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Preferred stock with mandatory redemption requirements, carrying amount	$ 13	$ 17
Long-term debt (excluding capital lease obligations), carrying amount	5,914	5,485
Preferred stock with mandatory redemption requirements, fair value	18	22
Long-term debt (excluding capital lease obligations), fair value	6,757	6,404
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt (excluding capital lease obligations), fair value	3,397	2,874
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt (excluding capital lease obligations), fair value	1,419	1,475
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Preferred stock with mandatory redemption requirements, fair value	18	22
Long-term debt (excluding capital lease obligations), fair value	$ 1,941	$ 2,055

Fair Value Measurements of Asse

Fair Value Measurements of Assets and Liabilities on Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Restricted funds	$ 27	$ 23
Rabbi trust investments	12	12
Deposits	1	4
Mark-to-market derivative asset	2	4
Other investments	4	22
Total assets	46	65
Deferred compensation obligation	11	12
Mark-to-market derivative liability	1	1
Total liabilities	12	13
Total net assets	34	52
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Restricted funds	27	23
Rabbi trust investments	12
Deposits	1	4
Other investments	4	22
Total assets	44	49
Deferred compensation obligation	11
Total liabilities	11
Total net assets	33	49
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Rabbi trust investments		12
Mark-to-market derivative asset	2	4
Total assets	2	16
Deferred compensation obligation		12
Mark-to-market derivative liability	1	1
Total liabilities	1	13
Total net assets	$ 1	$ 3

Fair Values of Financial Ins111

Fair Values of Financial Instruments - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Long term restricted funds	$ 6	$ 9

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating and Capital Leases [Line Items]
Rental expenses under operating leases	$ 21	$ 22	$ 23
Capital lease asset	156	$ 157
Minimum annual future rental commitment, 2016	13
Minimum annual future rental commitment, 2017	12
Minimum annual future rental commitment, 2018	11
Minimum annual future rental commitment, 2019	10
Minimum annual future rental commitment, 2020	8
Minimum annual future rental commitment, thereafter	$ 74
Minimum
Operating and Capital Leases [Line Items]
Operating leases renewal term, years	1 year
Maximum
Operating and Capital Leases [Line Items]
Operating leases renewal term, years	5 years
Equipment
Operating and Capital Leases [Line Items]
Operating leases expiration term, years	5 years
Facilities
Operating and Capital Leases [Line Items]
Operating leases expiration term, years	25 years
Minimum annual future rental commitment, 2016	$ 4
Minimum annual future rental commitment, 2017	4
Minimum annual future rental commitment, 2018	4
Minimum annual future rental commitment, 2019	4
Minimum annual future rental commitment, 2020	4
Minimum annual future rental commitment, thereafter	$ 69
Utilities
Operating and Capital Leases [Line Items]
Operating leases expiration term, years	40 years

Schedule of Minimum Annual Futu

Schedule of Minimum Annual Future Rental Commitment Under Operating Leases (Details) $ in Millions	Dec. 31, 2015USD ($)
Leases [Abstract]
2,016	$ 13
2,017	12
2,018	11
2,019	10
2,020	8
Thereafter	$ 74

Segment Information - Additiona

Segment Information - Additional Information (Details)	12 Months Ended
	Dec. 31, 2015Segment
Segment Reporting [Abstract]
Number of non-reportable operating segments for market-based businesses	4
Number of Reportable Segments	1
Segment Reporting, Additional Information about Entity's Reportable Segments	The Regulated Businesses segment is the largest component of the Company’s business and includes 18 subsidiaries that provide water and wastewater services to customers in 16 states.
Agreements range	50 years

Summarized Segment Information

Summarized Segment Information (Details) - USD ($)	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information [Line Items]
Operating revenues	$ 783,000,000	$ 896,000,000	$ 782,000,000	$ 698,000,000	$ 731,000,000		$ 846,000,000	$ 755,000,000	$ 679,000,000	$ 3,159,000,000	$ 3,011,000,000		$ 2,879,000,000	[1]
Depreciation and amortization										440,000,000	424,000,000		407,000,000	[1]
Total operating expenses, net										2,084,000,000	2,008,000,000		1,931,000,000	[1]
Interest, net										308,000,000	299,000,000		308,000,000
Income from continuing operations before income taxes										782,000,000	710,000,000		608,000,000	[1]
Provision for income taxes										306,000,000	280,000,000		237,000,000
Income from continuing operations										476,000,000	430,000,000		371,000,000
Total assets	17,241,000,000				16,038,000,000	[2]				17,241,000,000	16,038,000,000	[2]	15,064,000,000	[2]
Assets of discontinued operations (included in total assets above)	0				0					0	0		8,000,000
Capital expenditures										1,160,000,000	956,000,000		980,000,000
Capital expenditures of discontinued operations (included in capital expenditures above)													1,000,000
Operating Segments | Regulated Businesses
Segment Reporting Information [Line Items]
Operating revenues										2,743,000,000	2,674,000,000		2,594,000,000	[1]
Depreciation and amortization										411,000,000	394,000,000		376,000,000	[1]
Total operating expenses, net										1,732,000,000	1,726,000,000		1,700,000,000	[1]
Interest, net										248,000,000	248,000,000		249,000,000
Income from continuing operations before income taxes										776,000,000	707,000,000		655,000,000	[1]
Provision for income taxes										303,000,000	273,000,000		255,000,000
Income from continuing operations										473,000,000	434,000,000		400,000,000
Total assets	15,258,000,000				14,343,000,000	[2]				15,258,000,000	14,343,000,000	[2]	13,448,000,000	[2]
Capital expenditures										1,143,000,000	946,000,000		973,000,000
Operating Segments | Market-Based Businesses
Segment Reporting Information [Line Items]
Operating revenues										434,000,000	355,000,000		303,000,000	[1]
Depreciation and amortization										8,000,000	6,000,000		6,000,000	[1]
Total operating expenses, net										370,000,000	300,000,000		252,000,000	[1]
Interest, net										(2,000,000)	(2,000,000)		(2,000,000)
Income from continuing operations before income taxes										68,000,000	58,000,000		53,000,000	[1]
Provision for income taxes										26,000,000	18,000,000		14,000,000
Income from continuing operations										42,000,000	40,000,000		39,000,000
Total assets	496,000,000				314,000,000	[2]				496,000,000	314,000,000	[2]	286,000,000	[2]
Assets of discontinued operations (included in total assets above)													8,000,000
Capital expenditures										17,000,000	10,000,000		7,000,000
Capital expenditures of discontinued operations (included in capital expenditures above)													1,000,000
Other
Segment Reporting Information [Line Items]
Operating revenues										(18,000,000)	(18,000,000)		(18,000,000)	[1]
Depreciation and amortization										21,000,000	24,000,000		25,000,000	[1]
Total operating expenses, net										(18,000,000)	(18,000,000)		(21,000,000)	[1]
Interest, net										62,000,000	53,000,000		61,000,000
Income from continuing operations before income taxes										(62,000,000)	(55,000,000)		(100,000,000)	[1]
Provision for income taxes										(23,000,000)	(11,000,000)		(32,000,000)
Income from continuing operations										(39,000,000)	(44,000,000)		(68,000,000)
Total assets	$ 1,487,000,000				$ 1,381,000,000	[2]				$ 1,487,000,000	$ 1,381,000,000	[2]	$ 1,330,000,000	[2]
[1]	The information has been revised to reflect the impact of discontinued operations, as applicable. See Note 3—Acquisitions and Divestitures for additional details on the Company’s discontinued operations.
[2]	The information has been revised to reflect the retrospective application of ASU 2015-15 Presentation of Debt Issuance Costs and ASU 2015-17 Income Taxes. See Note 2–Significant Accounting Policies for additional details.

Schedule Of Unaudited Quarterly

Schedule Of Unaudited Quarterly Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Operating revenues	$ 783	$ 896	$ 782	$ 698	$ 731	$ 846	$ 755	$ 679	$ 3,159		$ 3,011		$ 2,879	[1]
Operating income	232	361	278	204	224	337	255	187	1,075		1,003		948
Net income attributable to common stockholders	$ 99	$ 174	$ 123	$ 80	$ 94	$ 152	$ 109	$ 68	$ 476		$ 423		$ 369
Basic earnings per share:
Net income attributable to common stockholders	$ 0.55	$ 0.97	$ 0.69	$ 0.45	$ 0.52	$ 0.85	$ 0.61	$ 0.38	$ 2.66	[2]	$ 2.36	[2]	$ 2.08	[2]
Diluted earnings per share:
Net income attributable to common stockholders	$ 0.55	$ 0.96	$ 0.68	$ 0.44	$ 0.52	$ 0.85	$ 0.61	$ 0.38	$ 2.64	[2]	$ 2.35	[2]	$ 2.06	[2]
[1]	The information has been revised to reflect the impact of discontinued operations, as applicable. See Note 3—Acquisitions and Divestitures for additional details on the Company’s discontinued operations.
[2]	Amounts may not sum due to rounding.