American Water Works (AWK) 10-K25 Feb 152014 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
Document and Entity Information (USD $)	Dec. 31, 2014	Feb. 19, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	AWK
Entity Registrant Name	American Water Works Company, Inc.
Entity Central Index Key	1410636
Current Fiscal Year End Date	-19
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		179,787,780
Entity Public Float			$8,858,523,983

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property plant and equipment
Utility plantâ€”at original cost, net of accumulated depreciation of $3,991,680 in 2014 and $3,894,326 in 2013	$12,899,704	$12,244,359
Nonutility property, net of accumulated depreciation of $248,341 in 2014 and $215,083 in 2013	129,592	143,995
Total property, plant and equipment	13,029,296	12,388,354
Current assets
Cash and cash equivalents	23,080	26,964
Restricted funds	13,859	28,505
Accounts receivable	267,053	241,926
Allowance for uncollectible accounts	-34,941	-33,823
Unbilled revenues	220,538	215,725
Income taxes receivable	2,575	5,778
Materials and supplies	37,190	32,973
Deferred income taxes	86,601	17,722
Assets of discontinued operations		7,761
Other	45,414	28,276
Total current assets	661,369	571,807
Regulatory and other long-term assets
Regulatory assets	1,153,429	858,465
Restricted funds	8,958	754
Goodwill	1,208,043	1,207,764
Other	69,861	60,998
Total regulatory and other long-term assets	2,440,291	2,127,981
TOTAL ASSETS	16,130,956	15,088,142
Capitalization
Common stock ($0.01 par value, 500,000 shares authorized, 179,462 shares outstanding in 2014 and 178,379 in 2013)	1,795	1,784
Paid-in-capital	6,301,729	6,261,396
Accumulated deficit	-1,295,549	-1,495,698
Accumulated other comprehensive loss	-81,868	-34,635
Treasury stock	-10,516	-5,043
Total common stockholders' equity	4,915,591	4,727,804
Long-term debt
Long-term debt	5,432,744	5,212,881
Redeemable preferred stock at redemption value	15,501	17,177
Total capitalization	10,363,836	9,957,862
Current liabilities
Short-term debt	449,959	630,307
Current portion of long-term debt	61,132	14,174
Accounts payable	285,800	264,115
Taxes accrued	24,505	32,166
Interest accrued	56,523	52,087
Liabilities of discontinued operations		3,824
Other	363,079	238,860
Total current liabilities	1,240,998	1,235,533
Regulatory and other long-term liabilities
Advances for construction	367,693	375,729
Deferred income taxes	2,120,739	1,840,697
Deferred investment tax credits	25,014	26,408
Regulatory liabilities	391,782	373,319
Accrued pension	316,368	108,542
Accrued postretirement benefit	192,502	88,419
Other	37,152	38,929
Total regulatory and other long-term liabilities	3,451,250	2,852,043
Contributions in aid of construction	1,074,872	1,042,704
Commitments and contingencies (See Note 14)
TOTAL CAPITALIZATION AND LIABILITIES	$16,130,956	$15,088,142

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]
Utility plant, accumulated depreciation	$3,991,680	$3,894,326
Nonutility property, accumulated depreciation	$248,341	$215,083
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares outstanding	179,462,000	178,379,000

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Operating revenues	$3,011,328		$2,878,936		$2,853,926
Operating expenses
Operation and maintenance	1,349,864		1,289,081		1,329,500
Depreciation and amortization	424,084		406,717		380,402
General taxes	236,732		234,198		220,758
(Gain) loss on asset dispositions and purchases	-1,928		624		-838
Total operating expenses, net	2,008,752		1,930,620		1,929,822
Operating income	1,002,576		948,316		924,104
Other income (expenses)
Interest, net	-297,818		-308,164		-310,794
Loss on extinguishment of debt			-40,583
Amortization of debt expense	-7,026		-6,603		-5,358
Other, net	-3,196		-4,045		-926
Total other income (expenses)	-292,762		-340,379		-293,715
Income from continuing operations before income taxes	709,814		607,937		630,389
Provision for income taxes	279,973		237,093		256,787
Income from continuing operations	429,841		370,844		373,602
Loss from discontinued operations, net of tax	-6,733		-1,580		-15,532
Net income	423,108		369,264		358,070
Other comprehensive income (loss), net of tax:
Change in employee benefit plan funded status, net of tax of $(29,487), $46,974 and $(16,894), respectively	-46,119		73,472		-26,425
Pension amortized to periodic benefit cost:
Prior service cost, net of tax of $106, $111 and $113, respectively	166		174		176
Actuarial (gain) loss, net of tax of $(19), $5,697 and $4,668, respectively	-31		8,911		7,301
Foreign currency translation adjustment	-458		-1,001		434
Unrealized loss on cash flow hedge, net of tax of $(428)	-791
Other comprehensive income (loss)	-47,233		81,556		-18,514
Comprehensive income	375,875		450,820		339,556
Basic earnings per share:
Income from continuing operations	$2.40	[1],[2]	$2.08	[1],[2]	$2.12	[1],[2]
Loss from discontinued operations, net of tax	($0.04)	[1],[2]	($0.01)	[1],[2]	($0.09)	[1],[2]
Net income	$2.36	[1],[2]	$2.08	[1],[2]	$2.03	[1],[2]
Diluted earnings per share:
Income from continuing operations	$2.39	[1],[2]	$2.07	[1],[2]	$2.10	[1],[2]
Loss from discontinued operations, net of tax	($0.04)	[1],[2]	($0.01)	[1],[2]	($0.09)	[1],[2]
Net income	$2.35	[1],[2]	$2.06	[1],[2]	$2.01	[1],[2]
Average common shares outstanding during the period
Basic	178,888		177,814		176,445
Diluted	179,806		179,056		177,671
Dividends declared per common share	$1.24		$1.12		$0.98
Other Funds
Other income (expenses)
Allowance for funds used during construction	9,440		12,639		15,592
Borrowed Funds
Other income (expenses)
Allowance for funds used during construction	$5,838		$6,377		$7,771

[1]	Amounts may not sum due to rounding
[2]	Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.

Consolidated_Statements_of_Ope1

Consolidated Statements of Operations and Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Change in employee benefit plan funded status, tax	($29,487)	$46,974	($16,894)
Prior service cost, tax	106	111	113
Actuarial (gain) loss, tax	-19	5,697	4,668
Unrealized loss on cash flow hedge, tax	($428)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$423,108	$369,264	$358,070
Adjustments
Depreciation and amortization	424,084	407,718	381,503
Provision for deferred income taxes	255,573	250,500	200,440
Amortization of deferred investment tax credits	-1,394	-1,501	-1,518
Provision for losses on accounts receivable	36,587	26,953	26,701
(Gain) loss on asset dispositions and purchases	-1,928	925	-839
Pension and non-pension postretirement benefits	24,073	78,069	87,289
Stock-based compensation expense	13,043	12,474	11,470
Other, net	-17,727	-727	-1,328
Changes in assets and liabilities
Receivables and unbilled revenues	-61,942	-79,306	-34,528
Taxes receivable, including income taxes	3,203	3,816	-1,922
Other current assets	-1,858	672	-5,223
Pension and non-pension postretirement benefit contributions	-52,195	-97,500	-129,410
Accounts payable	-26,137	16,215	-10,572
Taxes accrued, including income taxes	-7,895	-30,182	48,440
Interest accrued	4,436	-1,723	-5,647
Change in book overdraft	31,677	-32,120	34,172
Other current liabilities	62,019	-14,746	14,092
Net cash provided by operating activities	1,097,287	896,162	955,598
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	-956,119	-980,252	-928,574
Acquisitions	-8,935	-23,658	-44,560
Proceeds from sale of assets and securities	13,841	918	561,739
Removal costs from property, plant and equipment retirements, net	-78,175	-64,727	-57,101
Net funds released	15,399	14,425	86,140
Net cash used in investing activities	-1,013,989	-1,053,294	-382,356
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	500,497	404,157	315,430
Repayment of long-term debt	-238,371	-493,095	-471,954
Proceeds from short-term borrowings with maturities greater than three months	35,000	221,000
Repayments of short-term borrowings with maturities greater than three months	-256,000
Net short-term borrowings (repayments) with maturities less than three months	40,652	139,322	-211,064
Proceeds from issuances of employee stock plans and DRIP	20,913	26,351	27,860
Advances and contributions for construction, net of refunds of $21,470 in 2014, $23,351 in 2013 and $17,850 in 2012	26,295	19,251	31,909
Change in bank overdraft position			-34,812
Debt issuance costs	-4,593	-4,503	-7,393
Redemption of preferred stock	-1,650	-3,370	-4,376
Dividends paid	-216,354	-149,450	-213,459
Other	6,429		4,843
Net cash provided by (used in) financing activities	-87,182	159,663	-563,016
Net increase (decrease) in cash and cash equivalents	-3,884	2,531	10,226
Cash and cash equivalents at beginning of period	26,964	24,433	14,207
Cash and cash equivalents at end of period	23,080	26,964	24,433
Cash paid during the year for:
Interest, net of capitalized amount	301,138	317,826	329,331
Income taxes, net of refunds of $3,668 in 2014, $127 in 2013 and $766 in 2012	15,917	7,788	5,352
Non-cash investing activity:
Capital expenditures acquired on account but unpaid as of year end	185,641	128,902	159,119
Non-cash financing activity:
Advances and contributions	16,235	17,590	12,279
Dividends accrued	55,552	49,909
Long-term debt issued	9,977	6,702	68,746
Long-term debt retired	1,021	-3,565
Other Funds
Adjustments
Allowance for other funds used during construction	($9,440)	($12,639)	($15,592)

Consolidated_Statements_of_Cas1

Consolidated Statements of Cash Flows (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement Of Cash Flows [Abstract]
Advances and contributions for construction, refunds	$21,470	$23,351	$17,850
Income taxes, refunds	$3,668	$127	$766

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders' Equity (USD $)	Total	Common Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Treasury Stock	Preferred Stock of Subsidiary Companies Without Mandatory Redemption Requirements
In Thousands	Total	Common Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning Balance at Dec. 31, 2011	$4,240,384	$1,757	$6,180,558	($1,848,801)	($97,677)		$4,547
Beginning Balance (in shares) at Dec. 31, 2011		175,664
Net income	358,070			358,070
Direct stock reinvestment and purchase plan, net of expense	2,092		2,092
Direct stock reinvestment and purchase plan, net of expense (in shares)		60
Employee stock purchase plan	4,353	1	3,306			1,046
Employee stock purchase plan (in shares)		87				31
Stock-based compensation activity	34,486	12	36,688	-1,168		-1,046
Stock-based compensation activity (in shares)		1,177				-31
Subsidiary preferred stock redemption	-2,827						-2,827
Other comprehensive income (loss), net of tax	-18,514				-18,514
Dividends	-173,056			-173,056
Ending Balance at Dec. 31, 2012	4,444,988	1,770	6,222,644	-1,664,955	-116,191		1,720
Ending Balance (in shares) at Dec. 31, 2012		176,988
Net income	369,264			369,264
Direct stock reinvestment and purchase plan, net of expense	2,123	1	2,122
Direct stock reinvestment and purchase plan, net of expense (in shares)	53	53
Employee stock purchase plan	4,555	1	4,554
Employee stock purchase plan (in shares)		111
Stock-based compensation activity	26,397	12	32,076	-648		-5,043
Stock-based compensation activity (in shares)		1,227				-132
Subsidiary preferred stock redemption	-1,720						-1,720
Other comprehensive income (loss), net of tax	81,556				81,556
Dividends	-199,359			-199,359
Ending Balance at Dec. 31, 2013	4,727,804	1,784	6,261,396	-1,495,698	-34,635	-5,043
Ending Balance (in shares) at Dec. 31, 2013		178,379				-132
Net income	423,108			423,108
Direct stock reinvestment and purchase plan, net of expense	2,087	1	2,086
Direct stock reinvestment and purchase plan, net of expense (in shares)	44	44
Employee stock purchase plan	4,822	1	4,821
Employee stock purchase plan (in shares)		102
Stock-based compensation activity	27,000	9	33,426	-962		-5,473
Stock-based compensation activity (in shares)		937				-129
Other comprehensive income (loss), net of tax	-47,233				-47,233
Dividends	-221,997			-221,997
Ending Balance at Dec. 31, 2014	$4,915,591	$1,795	$6,301,729	($1,295,549)	($81,868)	($10,516)
Ending Balance (in shares) at Dec. 31, 2014		179,462				-261

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other comprehensive income (loss), tax	($29,828)	$52,782	($12,113)
DRIP Accounts
Stock issuance expense	$33	$49	$14

Organization_and_Operation

Organization and Operation	12 Months Ended
Organization and Operation	Dec. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Operation	Note 1: Organization and Operation
Organization and Operation	American Water Works Company, Inc. (“AWW”) and its subsidiaries (collectively referred to herein as the “Company”) is the holding company for regulated and market-based subsidiaries throughout the United States of America and one Canadian province. The regulated subsidiaries provide water and wastewater services as public utilities in 16 U.S. states. The market-based subsidiaries include various lines of business including Homeowner Services, which provides water and sewer line protection plans for homeowners; Military Services Group, which conducts operation and maintenance of water and wastewater systems for military bases; and the Contract Operations Group, which conducts operation and maintenance of water and wastewater facilities for municipalities and the food and beverage industry.

Significant_Accounting_Policie

Significant Accounting Policies	12 Months Ended
Significant Accounting Policies	Dec. 31, 2014
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2: Significant Accounting Policies
	Principles of Consolidation
	The accompanying consolidated financial statements include the accounts of AWW and its subsidiaries. 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 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 earnings as earnings or losses of investee.
	Use of Estimates
	The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States 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 benefit plan assumptions; the estimates used in impairment testing of goodwill and other long-lived assets, including regulatory assets; revenue recognition; and accounting for income taxes to be its critical accounting estimates. The Company’s significant accounting estimates that are particularly sensitive to change in the near term are amounts reported for pension and other postemployment benefits, 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 have allowed recovery of costs and credits which the Company has recorded as regulatory assets and liabilities. Accounting for future recovery of costs and credits as regulatory assets and liabilities is in accordance with authoritative guidance applicable to those companies whose rates are established by or are subject to approval by an independent third-party PUC. Regulated utilities defer costs and credits on the balance sheet as regulatory assets and liabilities when it is probable that those costs and credits will be recognized in the rate making process in a period different from the period in which they would have been reflected in operations by a market-based company. These deferred regulatory assets and liabilities are then reflected in the statement of operations in the period in which the costs and credits are reflected in the rates charged for service. (See Note 6)
	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. 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 $319,517 and $303,798 at December 31, 2014 and 2013, respectively.
	When units of property are replaced, retired or abandoned, the recorded value thereof 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.
	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 estimated useful lives of the assets, ranging from three to 50 years.
	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 of these financings are held in escrow until the designated expenditures are incurred. Classification of restricted funds in the balance sheet as either current or long-term is based upon the intended use of the funds.
	Accounts and Unbilled Receivables
	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 receivables 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 writes off accounts when they become uncollectible. (See Note 5)
	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. A provision is made to reduce excess or obsolete inventory to its net realizable value.
	Goodwill
	Goodwill is primarily associated with the acquisitions of AWW in 2003 and E’town Corporation in 2001 (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 Operations segment is comprised of three reporting units. Goodwill is tested annually or more frequently if changes in circumstances indicate goodwill may be impaired. Impairment exists when the carrying value of a reporting unit exceeds its fair value. Annual impairment tests are performed in the fourth quarter of the calendar year, in conjunction with the timing of the completion of the Company’s annual strategic business plan.
	The Company considers the carrying value of goodwill to be one of its critical accounting estimates. 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 considers the estimates used in the determination of fair value of long-lived assets to be one of its critical accounting estimates. 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.
	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 (“advances”) and contributions in aid of construction (“contributions”) 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 at December 31, 2014 and 2013 in the accompanying Consolidated Balance Sheets are estimated refunds of $18,366 and $17,308, 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 subsidiaries do not amortize contributions, and any contribution received remains on the balance sheet indefinitely. Amortization of contributions in aid of construction was $23,913, $22,363 and $20,979 for the years ended December 31, 2014, 2013 and 2012, 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 invoice to the end of the accounting period.
	The Company has agreements with the United States Government 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 operations and management components. The military agreements are subject to periodic price redetermination adjustments and modifications for changes in circumstance. Additionally, the Company has agreements ranging in length from two to 40 years with various industries and municipalities 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 14)
	Construction Contracts
	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
	AWW 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”)
	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.
	Environmental Costs
	The Company’s water and wastewater operations are subject to 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 $2,200 and $3,300 at December 31, 2014 and 2013, 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 $1,100 annually from 2010 to 2016. The Company pursues recovery of incurred costs through all appropriate means, including regulatory recovery through customer rates. The Company’s regulatory assets at December 31, 2014 and 2013 include $7,791 and $8,027, respectively, related to the NOAA agreement.
	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.
	New Accounting Standards
	The following recently issued accounting standards have been adopted by the Company and have been included in the consolidated results of operations, financial position or footnotes of the accompanying Consolidated Financial Statements:
	Obligations Resulting from Joint and Several Liability Arrangements
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued guidance for the recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. Examples of obligations within the scope of the updated guidance include debt arrangements, other contractual obligations and settled litigation and judicial rulings. The update requires an entity to measure obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of the following: (a) the amount the reporting entity agreed to pay on the basis of its arrangement among its co-obligors and (b) any additional amount the reporting entity expects to pay on behalf of its co-obligors. The updated guidance also includes additional disclosures regarding the nature and amount of the obligation, as well as other information about those obligations. The update was effective on a retrospective basis for interim and annual periods beginning after December 15, 2013, which for the Company was January 1, 2014. The adoption of this updated guidance did not have an impact on the Company’s results of operations, financial position or cash flows.
	Foreign Currency Matters
	In June 2013, the FASB issued guidance for a parent’s accounting for the cumulative translation adjustment upon derecognition of certain subsidiaries or groups of assets within a foreign entity or of an investment in a foreign entity. The amendments resolve differing views in practice and apply to the release of the cumulative translation adjustment into net income when a parent either sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or a business within a foreign entity. The update was effective prospectively for interim and annual periods beginning after December 15, 2013, which for the Company was January 1, 2014. The adoption of this updated guidance did not have an impact on the Company’s results of operations, financial position or cash flows.
	The following recently issued accounting standards are not yet required to be adopted by the Company:
Service Concession Arrangements
In January 2014, the FASB issued guidance for an operating entity that enters into a service concession arrangement with a public sector grantor who controls or has the ability to modify or approve the services that the operating entity must provide with the infrastructure, to whom it must provide the services and at what price. The grantor also controls, through ownership or otherwise, any residual interest in the infrastructure at the end of the term of the arrangement. The guidance specifies that an operating entity should not account for the service concession arrangement as a lease. The operating entity should refer instead to other accounting guidance to account for the various aspects of the arrangement. The guidance also specifies that the infrastructure used in the arrangement should not be recognized as property, plant and equipment of the operating entity. This update should be applied on a modified retrospective basis to service concession arrangements that exist at the beginning of an entity’s fiscal year of adoption. This requires the cumulative effect of applying the update to be recognized as an adjustment to the opening retained earnings balance for the annual period of adoption. The update is effective for interim and annual periods beginning after December 15, 2014, which for the Company is January 1, 2015. The adoption of this updated guidance resulted in a decrease to nonutility property and opening retained earnings of approximately $12,000 on January 1, 2015.
Reporting Discontinued Operations
In April 2014, the FASB issued guidance that changes the criteria for determining which disposals can be presented as discontinued operations and modifies related disclosure requirements. Under the updated guidance, 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. A strategic shift could include a disposal of a major geographical area of operations, a major line of business, a major equity method investment or other major part of the entity. A component comprises operations and cash flows that can be clearly distinguished, operationally and for financial reporting purposes, from the rest of the entity including a reportable segment, an operating segment, a reporting unit, a subsidiary or an asset group. 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. The updated guidance is effective on a prospective basis for interim and annual periods on or after December 15, 2014, which for the Company is January 1, 2015. In general, this guidance is likely to result in fewer disposals of assets qualifying as discontinued operations, but will ultimately be based on the Company’s future disposal activity.
Revenue from Contracts with Customers
In May 2014, the FASB issued a comprehensive new revenue recognition standard that supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the new guidance is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance is effective for annual and interim periods beginning December 15, 2016, which for the Company is January 1, 2017. Early adoption is not permitted. The new guidance allows for either full retrospective adoption, meaning the guidance is applied to all of the periods presented, or modified retrospective adoption, meaning the standard is applied only to the most current period presented in the financial statements. The Company is evaluating the new guidance, the best transition method and the impact the new standard will have on its results of operations, financial position or cash flows.
Accounting for Stock-based Compensation with Performance Targets
In June 2014, the FASB issued guidance for the accounting for stock-based compensation tied to performance targets. The amendments clarify that a performance target that affects vesting of a share-based payment and that could be achieved after the requisite service period is a performance condition. As a result, the target is not reflected in the estimation of the award’s grant date fair value and compensation cost would be recognized over the required service period, if it is probable that the performance condition will be achieved. The updated guidance may be applied either: (a) prospectively to all awards granted or modified after the effective date or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. The updated guidance is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, which for the Company is January 1, 2016. Early adoption is permitted. The Company is evaluating the impact the updated guidance will have on its results of operations, financial position or cash flows.
Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern
In August 2014, the FASB issued guidance that explicitly requires an entity’s management to assess the entity’s ability to continue as a going concern. The new guidance requires an entity to evaluate, at each interim and annual period, whether there are conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date the financial statements are issued (or are available to be issued) and to provide related disclosures, if applicable. The new guidance is effective for annual periods ending after December 15, 2016 and for interim and annual periods thereafter, which for the Company is January 1, 2017. Early adoption is permitted. The adoption of this updated guidance is not expected to have a material impact on results of operations, financial position or cash flows.
Hybrid Financial Instruments Issued in the Form of a Share
In November 2014, the FASB updated the derivatives and hedging guidance requiring issuers of, or investors in, hybrid financial instruments to determine whether the nature of the host contract is more akin to a debt instrument or an equity instrument by considering the economic characteristics and risks of the entire hybrid financial instrument, including the embedded derivative feature that is being evaluated for separate accounting from the host contract. This update should be applied on a modified retrospective basis to hybrid financial instruments issued in the form of a share that exist at the beginning of an entity’s fiscal year of adoption. The updated guidance is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, which for the Company is January 1, 2016. Early adoption is permitted. The Company is evaluating the impact the updated guidance will have on its results of operations, financial position or cash flows.
Extraordinary and Unusual Items
In January 2015, the FASB issued guidance that eliminates the concept of an extraordinary item. As a result, an entity will no longer segregate an extraordinary item and present it separately from the results of ordinary operations or separately disclose income taxes or earnings per share information applicable to an extraordinary item. The presentation and disclosure guidance for items that are unusual in nature or occur infrequently has been retained and expanded to include items that are both unusual in nature and infrequently occurring. The updated guidance is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, which for the Company is January 1, 2016. Early adoption is permitted. The updated guidance may be applied prospectively or retrospectively to all periods presented in the financial statements. The adoption of this updated guidance is not expected to have a material impact on results of operations, financial position or cash flows.
Reclassifications
In 2014 the Company reclassified previously reported data to conform to the current presentation for discontinued operations. See Note 3 for additional details on the Company’s discontinued operations.
In 2014 the Company revised its 2013 balance sheet to properly reclassify $17,722 of deferred income taxes from current liabilities to current assets. This reclassification was not material to the previously issued financial statements.

Acquisitions_and_Divestitures

Acquisitions and Divestitures	12 Months Ended
Acquisitions and Divestitures	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions and Divestitures	Note 3: Acquisitions and Divestitures
	Acquisitions
	During 2014, the Company closed on 13 acquisitions of various regulated water and wastewater systems for a total aggregate purchase price of $8,935. Assets acquired, principally plant, totaled $16,592 including $354 of goodwill and liabilities assumed totaled $7,745, including $4,741 of contributions in aid of construction and assumed debt of $1,683.
	During 2013, the Company closed on 15 acquisitions of various regulated water and wastewater systems for a total aggregate net purchase price of $23,658. Assets acquired (primarily utility plant) totaled $67,403, and liabilities assumed totaled $43,745, including $25,654 of contributions in aid of construction and assumed debt of $12,673. 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 $5,090 (net of cash acquired of $6,910), plus assumed liabilities. The Dale acquisition added approximately twenty thousand wastewater customers to the Company’s existing water services footprint in Northern Virginia. 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 has been followed whereby property, plant and equipment (rate base) is considered fair value for business combination purposes. Similarly, regulatory assets and liabilities acquired have been 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 16) Non-cash assets acquired in the Dale acquisition (primarily utility plant) totaled $40,999; liabilities assumed totaled $35,909, including debt assumed of $12,570 and contributions of $19,163.
	During 2012, the Company closed on 10 acquisitions of various regulated water and wastewater systems for a total aggregate purchase price of $44,560. Included in this total was the Company’s May 1, 2012 acquisition of all of the capital stock of Aqua New York, Inc. for a total cash purchase price of $36,688 plus assumed liabilities. Assets acquired in the Aqua New York acquisition totaled $102,727, including $59,139 of plant, $27,400 of regulatory assets, and $12,181 of goodwill; liabilities assumed totaled $66,039, including long-term debt of $25,215, $11,885 of regulatory liabilities, $15,424 of deferred taxes, $1,708 of other liabilities, $1,060 of contributions in aid of construction and $9,710 of pension and postretirement welfare liabilities. Assets acquired (primarily utility plant) in the other nine acquisitions during 2012 totaled $12,514; liabilities assumed totaled $4,642.
	Divestitures
	In November 2014, the Company completed the sale of Terratec, previously included in the Market-Based Operations segment. After post-close adjustments, net proceeds from the sale totaled $1,455, and the Company recorded a pretax loss on sale of $1,454.
	In January 2012, the Company completed the sale of its Arizona and New Mexico subsidiaries. After post-close adjustments, net proceeds from the sale totaled $458,860, and the Company recorded a pretax loss on sale of $2,198.
	In May 2012, the Company completed the sale of its Ohio subsidiary. After post-close adjustments, net proceeds from the sale totaled $102,154, and the Company recorded a pretax loss on sale of $4,095.
	A summary of discontinued operations presented in the Consolidated Statements of Operations and Comprehensive Income follows:

		Years Ended December 31,
		2014			2013			2012
	Operating revenues	$	13,614		$	22,922		$	42,341
	Total operating expenses, net		19,482			25,389			49,726
	Operating loss		(5,868	)		(2,467	)		(7,385	)
	Other income (expenses), net	—			—				(167	)
	Income (loss) from discontinued operations before		(5,868	)		(2,467	)		(7,552	)
	income taxes		(5,868	)		(2,467	)		(7,552	)
	Provision (benefit) for income taxes		865			(887	)		7,980
	Income (loss) from discontinued operations	$	(6,733	)	$	(1,580	)	$	(15,532	)
	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, Arizona, New Mexico and Ohio 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.
	Assets and liabilities of discontinued operations at December 31, 2013 relate to the discontinued Terratec business that was sold in November 2014. The classification for the year ended December 31, 2013 was as follows:

			2013
	ASSETS
	Total property, plant and equipment		$	2,808
	Current assets			4,953
	Total assets of discontinued operations		$	7,761

	LIABILITIES
	Current liabilities		$	3,824
	Total liabilities of discontinued operations		$	3,824

	There were no assets or liabilities of discontinued operations in the accompanying Consolidated Balance Sheet at December 31, 2014.

Utility_Plant

Utility Plant	12 Months Ended
Utility Plant	Dec. 31, 2014
Disclosure Components Of Utility Plant By Category [Abstract]
Utility Plant	Note 4: Utility Plant
	The major classes of utility plant by category at December 31 are as follows:

		Range of Remaining
		Useful Lives	2014		2013
	Water plant
	Land and other non-depreciable assets		$	137,199	$	132,295
	Sources of supply	11 to 127 Years		680,623		659,249
	Treatment and pumping facilities	3 to 101 Years		2,969,411		3,006,140
	Transmission and distribution facilities	9 to 156 Years		7,962,759		7,489,208
	Services, meters and fire hydrants	9 to 122 Years		3,062,568		2,898,293
	General structures and equipment	1 to 154 Years		1,035,857		995,186
	Wastewater plant	2 to 115 Years		739,963		683,112
	Construction work in progress			303,004		275,202
				16,891,384		16,138,685
	Less accumulated depreciation			3,991,680		3,894,326
			$	12,899,704	$	12,244,359

	Utility plant depreciation expense of continuing operations amounted to $356,952 in 2014, $337,653 in 2013 and $314,639 in 2012. 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.
	The provision for depreciation expressed as a percentage of the aggregate average depreciable asset balances was 2.94% in 2014, 2013 and 2012.

Allowance_for_Uncollectible_Ac

Allowance for Uncollectible Accounts	12 Months Ended
Allowance for Uncollectible Accounts	Dec. 31, 2014
Disclosure Schedule Of Allowances For Uncollectible Accounts [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:

		2014			2013			2012

	Balance at January 1	$	(33,823	)	$	(26,744	)	$	(18,902	)
	Amounts charged to expense		(36,717	)		(26,953	)		(26,701	)
	Amounts written off		42,886			23,914			22,607
	Recoveries of amounts written off		(7,287	)		(4,040	)		(3,748	)
	Balance at December 31	$	(34,941	)	$	(33,823	)	$	(26,744	)

Regulatory_Assets_and_Liabilit

Regulatory Assets and Liabilities	12 Months Ended
Regulatory Assets and Liabilities	Dec. 31, 2014
Disclosure Components Of Regulatory Assets Liabilities [Abstract]
Regulatory Assets and Liabilities	Note 6: Regulatory Assets and Liabilities
	The regulatory assets represent costs that are expected to be fully recovered from customers in future rates. Except for income taxes, regulatory assets are excluded from the Company’s rate base and generally do not earn a return. The components of regulatory assets at December 31 are as follows:

		2014		2013
	Income taxes recoverable through rates	$	228,601	$	242,902
	Debt and preferred stock expense		71,403		72,349
	Deferred pension expense		263,486		109,799
	Deferred other postretirement benefit expense		106,792		3,653
	Deferred business services project expense		7,530		7,763
	Deferred tank painting costs		37,207		33,519
	Deferred rate case expense		6,785		9,407
	Purchase premium recoverable through rates		60,412		60,787
	Environmental remediation recoverable through rates		7,791		8,027
	Coastal water project costs		8,386		16,826
	San Clemente Dam project costs		71,891		44,404
	Removal costs recoverable through rates		163,123		126,771
	Regulatory balancing accounts		60,043		63,083
	Other		59,979		59,175
		$	1,153,429	$	858,465
	The Company has recorded a regulatory asset for the additional revenues expected to be realized as 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.
	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. Expenses of preferred stock issues without sinking fund provisions are amortized over approximately 30 years from date of issue; expenses of issues with sinking fund provisions are charged to operations as shares are retired.
	Pension expense in excess of the amount contributed to the pension plans is deferred by certain subsidiaries. These costs will be recovered in future service rates as contributions are made to the pension plan. The Company also has a regulatory asset of $248,641 and $90,380 at December 31, 2014 and 2013, respectively, which is the portion of the underfunded status that is probable of recovery through rates in future periods.
	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. The Company also has a regulatory asset of $107,236 and $3,113 at December 31, 2014 and 2013, respectively, which is the portion of the underfunded status that is probable of recovery through rates in future periods.
	Business services project expenses consist of reengineering and start-up activities for consolidated customer and shared administrative service centers that began operations in 2001. These costs are recognized in the rates charged for water service by certain subsidiaries.
	Tank painting costs are generally deferred and amortized to current operations on a straight-line basis over periods ranging from five to 15 years, as authorized by the regulatory authorities in their determination of rates charged for service.
	The Company amortizes rate case expenditures over regulatory approved amortization periods, typically three years. Rate case proceeding expenditures probable of future recovery are deferred.
	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 operations through November 2048.
	Environmental remediation recoverable through rates is the recovery of costs incurred by the Company’s California subsidiary under a settlement agreement entered into with NOAA to improve habitat conditions in the Carmel River Watershed.
	Coastal water project costs include preliminary costs associated with the studying, testing and design of alternatives to help solve water supply shortages in Monterey, California. Coastal water project costs incurred through December 31, 2010 have been reviewed and approved for recovery through a surcharge. Costs deferred during 2014, 2013 and 2012 totaled $1,923, $1,299 and $1,987, respectively. The Company believes it is probable that the costs incurred since the last rate review will also be recoverable.
	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 all previous pre-construction costs incurred by the Company’s subsidiary, and has authorized additional expenditures to be capped at $49,000 for the reroute and dam removal efforts and $2,500 for estimated interim dam safety measures. All pre-construction costs, totaling $24,303, are to be recovered via a surcharge over a 20-year period beginning October 2012; surcharge collections in 2014 and 2013 totaled $4,531 and $3,753, respectively. Costs deferred in addition to the pre-construction costs totaled $26,023 and $12,394 as of December 31, 2014 and 2013, respectively.
	Regulatory balancing accounts accumulate differences between revenues 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.
	Other regulatory assets include certain deferred employee benefit costs which are deferred because the amounts are being recovered in rates or are probable of recovery through rates in future periods.
	The components of regulatory liabilities at December 31 are as follows:

		2014		2013

	Removal costs recovered through rates	$	300,635	$	301,537
	Pension and other postretirement benefit		53,734		40,837
	balancing accounts		53,734		40,837
	Other		37,413		30,945
		$	391,782	$	373,319

	Removal costs recovered through rates are retirement costs recovered during 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 amortize $48,000 of the total balance into 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.
	Other regulatory liabilities include legal settlement proceeds, deferred gains, future customer refunds, and various regulatory balancing accounts.

Goodwill

Goodwill	12 Months Ended
Goodwill	Dec. 31, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill	Note 7: Goodwill
	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 strategic business plan. The Company assesses qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. The Company also undertakes interim reviews when the Company determines that a triggering event that would more likely than not reduce the fair value of a reporting unit below its carrying value has occurred.
	After assessing various events and circumstances in 2014, 2013 and 2012, 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, 2014, 2013 and 2012.
	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 Company’s performance. 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, the lack of an increase in the Company’s market price consistent with its peer companies or decreases in control premiums. A decline in the forecasted results in the Company’s business plan, such as changes in rate case results or capital investment budgets or changes in the Company’s interest rates, could also result in an impairment charge.
	The changes in the Company’s carrying value of goodwill by reporting unit are as follows:

		Regulated Unit						Market-Based Operations					Consolidated
		Cost			Accumulated Impairment			Cost		Accumulated Impairment			Cost			Accumulated Impairment			Total Net
	Balance at January 1, 2013	$	3,411,549		$	(2,332,670	)	$	235,990	$	(107,619	)	$	3,647,539		$	(2,440,289	)	$	1,207,250
	Goodwill from acquisitions		428			—			—		—			428			—			428
	Reclassifications and other		86			—			—		—			86			—			86
	activity		86			—			—		—			86			—			86
	Balance at December 31, 2013	$	3,412,063		$	(2,332,670	)	$	235,990	$	(107,619	)	$	3,648,053		$	(2,440,289	)	$	1,207,764

	Goodwill from acquisitions		354			—			—		—			354			—			354
	Reclassifications and other		(75	)		—			—		—			(75	)		—			(75	)
	activity		(75	)		—			—		—			(75	)		—			(75	)
	Balance at December 31, 2014	$	3,412,342		$	(2,332,670	)	$	235,990	$	(107,619	)	$	3,648,332		$	(2,440,289	)	$	1,208,043

Stockholders_Equity

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2014
Equity [Abstract]
Stockholders' Equity	Note 8: Stockholders’ Equity
	Common Stock
	Under American Water Stock Direct, a 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. The Company’s plan administrator may buy newly issued shares directly from the Company or shares held in the Company’s treasury. The plan administrator may also buy shares in the public markets or in privately negotiated transactions. Purchases generally will be made and credited to DRIP accounts once each week. As of December 31, 2014, there were 4,611 shares available for future issuance under the DRIP. The following table summarizes information regarding issuances under the DRIP for the years ended December 31, 2014 and 2013:

		2014				2013
	Shares of common stock issued		44				53
	Cash proceeds received	$	2,119			$	2,171
	Cash dividend payments made during 2014 and 2013 were as follows:

		2014				2013
	Dividends per share, three months ended:
	31-Mar	$	0.28			$	—
	30-Jun		0.31				0.28
	30-Sep		0.31				0.28
	31-Dec		0.31				0.28

	Total dividends paid, three months ended:
	31-Mar	$	49,968			$	—
	30-Jun		55,422				49,744
	30-Sep		55,458				49,810
	31-Dec		55,506				49,896
	On December 12, 2014, the Company declared a quarterly cash dividend of $0.31 per share, payable on March 2, 2015 to shareholders of record as of February 9, 2015. As of December 31, 2014, the Company had accrued dividends totaling $55,552 included in other current liabilities on the accompanying Consolidated Balance Sheets.
	Accumulated Other Comprehensive Loss
	The following table presents changes in accumulated other comprehensive loss by component, net of tax:

		Defined Benefit Plans
		Employee Benefit Plan Funded Status				Amortization of Prior Service Cost				Amortization of Actuarial (Gain) Loss				Foreign Currency Translation			Loss on Cash Flow Hedge			Total Accumulated Other Comprehensive Loss
	Beginning balance at January 1, 2013	$	(143,183	)		$	539			$	22,239			$	4,214		$	—		$	(116,191	)
	Other comprehensive income (loss) before		73,472				—				—				(1,001	)		—			72,471
	reclassifications		73,472				—				—				(1,001	)		—			72,471
	Amounts reclassified from accumulated		—				174				8,911				—			—			9,085
	other comprehensive income (loss)		—				174				8,911				—			—			9,085
	Net comprehensive income (loss) for the		73,472				174				8,911				(1,001	)		—			81,556
	period		73,472				174				8,911				(1,001	)		—			81,556
	Ending balance at December 31, 2013	$	(69,711	)		$	713			$	31,150			$	3,213		$	—		$	(34,635	)
	Other comprehensive income (loss) before		(46,119	)			—				—				(458	)		(820	)		(47,397	)
	reclassifications		(46,119	)			—				—				(458	)		(820	)		(47,397	)
	Amounts reclassified from accumulated		—				166				(31	)			—			29			164
	other comprehensive income (loss)		—				166				(31	)			—			29			164
	Net comprehensive income (loss) for the		(46,119	)			166				(31	)			(458	)		(791	)		(47,233	)
	period		(46,119	)			166				(31	)			(458	)		(791	)		(47,233	)
	Ending balance at December 31, 2014	$	(115,830	)		$	879			$	31,119			$	2,755		$	(791	)	$	(81,868	)
	The Company does not reclassify the amortization of defined benefit pension cost components from accumulated other comprehensive income (loss) directly to net income in its entirety. These accumulated other comprehensive income (loss) components are included in the computation of net periodic pension cost. (See Note 13)
	The amortization of the loss on cash flow hedge is included in interest, net in the accompanying Consolidated Statements of Operations and Comprehensive Income.
	Stock Based Compensation
	The Company has granted stock option and restricted stock unit 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 “Plan”). The total aggregate number of shares of common stock that may be issued under the Plan is 15,500. As of December 31, 2014, a total of 8,869 shares were available for grant under the Plan. Shares issued under the 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 for purposes of the Plan.
	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 and Comprehensive Income for the years ended December 31, 2014, 2013 and 2012:

		2014				2013				2012
	Stock options	$	2,602			$	3,170			$	3,282
	Restricted stock units		9,848				8,718				7,658
	Employee stock purchase plan		593				586				530
	Stock-based compensation in operation and		13,043				12,474				11,470
	maintenance expense		13,043				12,474				11,470
	Income tax benefit		(5,087	)			(4,865	)			(4,473	)
	After-tax stock-based compensation expense	$	7,956			$	7,609			$	6,997
	There were no significant stock-based compensation costs capitalized during the years ended December 31, 2014, 2013 and 2012.
	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 restricted stock unit awards at the date of the grant is amortized through expense over the three-year service period. All awards granted in 2014, 2013 and 2012 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 restricted stock units. For each award, throughout the requisite service period, the Company recognizes the tax benefits, which have been included in deferred tax assets, related to compensation costs. The tax deductions in excess of the benefits recorded throughout the requisite service period are recorded to shareholders’ equity or the income statement and are included in the financing section of the statement 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 period and adjusted as necessary.
	Stock Options
	In 2014, 2013 and 2012, the Company granted non-qualified stock options to certain employees under the Plan. The stock options vest ratably over the three-year service period beginning on January 1 of the year of 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.
	The following table presents 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 in the years ended December 31, 2014, 2013 and 2012:

	2014				2013				2012
Dividend yield		2.55	%			2.52	%			2.7	%
Expected volatility		17.75	%			23.5	%			28.35	%
Risk-free interest rate		1.06	%			0.7	%			0.78	%
Expected life (years)		3.6				4.3				4.4
Exercise price	$	44.29			$	39.6			$	34.14
Grant date fair value per share	$	4.57			$	5.78			$	6.11
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 expire seven years from the effective date of the grant. The fair value of each option is estimated on the date of grant using the Black-Scholes option-pricing model.
The value of stock options at the date of the grant is amortized through expense over the requisite service period using the straight-line method. As of December 31, 2014, $1,545 of total unrecognized compensation cost related to nonvested stock options is expected to be recognized over the remaining weighted-average period of 1.7 years. The total grant date fair value of stock options vested during the years ended December 31, 2014, 2013 and 2012 was $2,728, $3,512 and $3,219, respectively.
The table below summarizes stock option activity for the year ended December 31, 2014:

	Shares				Weighted-Average Exercise Price (per share)				Weighted-Average Remaining Life (years)				Aggregate Intrinsic Value
Options outstanding at January 1, 2014		2,055			$	28.8
Granted		491				44.29
Forfeited or expired		(62	)			39.23
Exercised		(574	)			25.4
Options outstanding at December 31, 2014		1,910			$	33.47				3.9			$	37,881
Exercisable at December 31, 2014		1,094			$	27.68				2.8			$	28,022
The following table summarizes additional information regarding stock options exercised during the years ended December 31, 2014, 2013 and 2012:

	2014				2013				2012
Intrinsic value	$	12,689			$	15,102			$	14,515
Exercise proceeds		14,582				20,211				22,112
Income tax benefit		3,885				4,383				4,017
Restricted Stock Units
During 2011, the Company granted selected employees 189 restricted stock units with internal performance measures and, separately, certain market thresholds. These awards vested in January 2014. The terms of the grants specified that if certain performance on internal measures and market thresholds was achieved, the restricted stock units would vest; if performance was surpassed, up to 175% of the target awards would be distributed; and if performance thresholds were not met, awards would be cancelled. In January 2014, an additional 113 restricted stock units were granted and distributed because performance thresholds were exceeded.
In 2014, 2013 and 2012, the Company granted restricted stock units, both with and without performance conditions, to certain employees under the Plan. The restricted stock units without performance conditions vest ratably over the three-year service period beginning January 1 of the year of the grant and the restricted stock units with performance conditions vest ratably over the three-year performance period beginning January 1 of the year of 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 2014, 2013 and 2012, the Company granted restricted stock units to non-employee directors under the Plan. The restricted stock units vested on the date of grant; however, distribution of the shares will be made within 30 days of the earlier of (a) 15 months after grant date or (b) the participant’s separation from service. Because these restricted stock units vested on 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.
Restricted stock units generally vest over periods ranging from one to three years. Restricted stock units granted with service-only conditions and those with internal performance measures are valued at the market value of the Company’s common stock on the date of grant. Restricted stock units 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 restricted stock units granted during the years ended December 31, 2014, 2013 and 2012:

	2014				2013				2012
Expected volatility		17.78	%			19.37	%			22.47	%
Risk-free interest rate		0.75	%			0.4	%			0.43	%
Expected life (years)		3				3				3
Grant date fair value per share	$	45.45			$	40.13			$	37.4
The grant date fair value of restricted stock awards that vest ratably and have market and/or performance and service conditions is amortized through expense over the requisite service period using the graded-vesting method. Restricted stock units that have no performance conditions are amortized through expense over the requisite service period using the straight-line method. As of December 31, 2014, $4,634 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 restricted stock units vested during the years ended December 31, 2014, 2013 and 2012 was $10,829, $8,891 and $4,191, respectively.
The table below summarizes restricted stock unit activity for the year ended December 31, 2014:

	Shares				Weighted-Average Grant Date Fair Value (per share)
Non-vested total at January 1, 2014		539			$	36.27
Granted		228				45.45
Performance share adjustment		113				30.34
Vested		(337	)			32.13
Forfeited		(27	)			41.61
Non-vested total at December 31, 2014		516			$	41.46
The following table summarizes additional information regarding restricted stock units distributed during the years ended December 31, 2014, 2013 and 2012:

	2014				2013				2012
Intrinsic value	$	15,539			$	13,983			$	6,159
Income tax benefit		1,625				2,049				799
If dividends are paid with respect to shares of the Company’s common stock before the restricted stock units are distributed, the Company credits a liability for the value of the dividends that would have been paid if the restricted stock units were shares of Company common stock. When the restricted stock units 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 $962, $648 and $1,168 to retained earnings during the years ended December 31, 2014, 2013 and 2012, 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 (a) the beginning or (b) the end of each three-month purchase period. As of December 31, 2014, there were 1,261 shares of common stock reserved for issuance under the ESPP. The Company’s ESPP is considered compensatory. During the years ended December 31, 2014, 2013 and 2012, the Company issued 102, 111 and 118 shares, respectively, under the ESPP.

LongTerm_Debt

Long-Term Debt	12 Months Ended
Long-Term Debt	Dec. 31, 2014
Debt Disclosure [Abstract]
Long-Term Debt	Note 9: Long-Term Debt
	The Company primarily incurs long-term debt to fund capital expenditures of the regulated subsidiaries. The components of long-term at December 31 are:

		Rate				Weighted Average Rate				Maturity			2014		2013

	Long-term debt of American Water Capital Corp.
	("AWCC") (a)
	Private activity bonds and government funded
	debt
	Fixed rate	1.79%-6.25%					5.33%			2021-2040		$	231,330	$	330,732
	Senior notes
	Fixed rate	3.40%-8.27%					5.43%			2016-2042			3,753,200		3,312,761
	Long-term debt of other subsidiaries
	Private activity bonds and government funded
	debt
	Fixed rate (b)	0.00%-6.20%					4.73%			2015-2041			795,472		863,716
	Mortgage bonds
	Fixed rate	4.29%-9.71%					7.41%			2015-2039			676,500		676,500
	Mandatorily redeemable preferred stock	8.47%-9.75%					8.60%			2019-2036			17,252		18,902
	Capital lease obligations		12.17%				12.17%			2026			885		913
	Long-term debt												5,474,639		5,203,524
	Unamortized debt, net (c)												31,168		35,984
	Interest rate swap fair value adjustment												3,570		4,724
	Total long-term debt											$	5,509,377	$	5,244,232


	(a)	AWCC, which is a wholly-owned subsidiary of the Company, has a strong support agreement with its parent that, under certain circumstances, is the functional equivalent of a guarantee.
	(b)	Includes $10,190 and $11,920 of variable rate debt with variable-to-fixed interest rate swaps ranging between 3.93% and 4.72%, at December 31, 2014 and 2013, respectively. This debt was assumed via an acquisition in 2013.
	(c)	Primarily fair value adjustments previously recognized in acquisition purchase accounting.
	All $676,500 of the subsidiaries’ mortgage bonds and $729,170 of the $795,472 total subsidiaries’ private activity bonds and government funded debt at December 31, 2014 are collateralized by utility plant.
	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 at December 31, 2014 was 0.55 to 1.00. In addition, the Company has $1,044,990 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 are as follows:


	Year		Amount
	2015		$	61,132
	2016			53,353
	2017			572,775
	2018			455,861
	2019			164,909
	Thereafter			4,166,609
	The following long-term debt was issued in 2014:

	Company		Type		Rate		Maturity		Amount
	AWCC		Senior notes—fixed rate		3.40%-4.30%		2025-2042		$	500,000
	Other subsidiaries (1)		Private activity bonds and government funded debt—fixed rate		0.00%-5.00%		2031-2033			10,474
	Total issuances								$	510,474


	-1	Included in the issuance amounts for other subsidiaries private activity bonds and government funded debt above was $9,977, which was initially kept in Trust pending the Company’s certification that it has incurred qualifying capital expenditures. These issuances have been presented as non-cash in the accompanying Consolidated Statements of Cash Flows. Subsequent releases of all or a lesser portion of these funds by the applicable Trust are reflected as the release of restricted funds and are included in investing activities in the accompanying Consolidated Statements of Cash Flows.
	The Company incurred debt issuance costs of $4,593 related to the above issuances. The Company also assumed debt of $1,683 via an acquisition during 2014.
	The following long-term debt was retired through optional redemption or payment at maturity during 2014:

	Company		Type		Rate				Maturity		Amount
	AWCC		Private activity bonds and government		6.00%-6.75%				2018-2032		$	101,085
	AWCC		funded debt—fixed rate		6.00%-6.75%				2018-2032		$	101,085
	AWCC		Senior notes—fixed rate			6.00%			2039			59,561
	Other subsidiaries (1)		Private activity bonds and government		0.00%-5.25%				2014-2041			78,718
	Other subsidiaries (1)		funded debt—fixed rate		0.00%-5.25%				2014-2041			78,718
	Other subsidiaries		Mandatorily redeemable preferred stock		8.49%-9.18%				2031-2036			1,650
	Other subsidiaries		Capital lease payments									28
	Total retirements and redemptions										$	241,042


-1	Includes $1,021 of non-cash defeasance via the use of restricted funds.
Interest, net includes interest income of approximately $11,441, $11,753 and $12,652 in 2014, 2013 and 2012, 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 $100,000 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, 2014 and 2013, and the line items in the Consolidated Balance Sheets in which such amounts are recorded:

Balance sheet classification		2014				2013
Regulatory and other long-term assets
Other		$	3,636			$	4,776
Long-term debt
Long-term debt			3,570				4,724

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 as follows:


Income statement classification		2014				2013				2012
Interest, net
Gain (loss) on swap		$	(1,140	)		$	(3,133	)		$	2,085
Gain (loss) on borrowing			1,154				2,991				(1,604	)
Hedge ineffectiveness			14				(142	)			481

ShortTerm_Debt

Short-Term Debt	12 Months Ended
Short-Term Debt	Dec. 31, 2014
Short Term Borrowings [Abstract]
Short-Term Debt	Note 10: Short-Term Debt
	Short-term debt consists of commercial paper borrowings totaling $449,959 (net of discount of $41) and $630,307 (net of discount of $193) at December 31, 2014 and 2013, respectively. At December 31, 2014 there were no borrowings outstanding with maturities greater than three months.
	On September 9, 2013, AWCC and its lenders agreed to increase total commitments under AWCC’s revolving credit facility from $1,000,000 to $1,250,000. In addition, $1,180,000 of the credit facility was extended from its original termination date of October 2017 to October 2018. Other terms and conditions of the existing facility remained unchanged. The Company incurred $1,126 of issuance costs in connection with the increased lending commitments; these costs will be amortized over the remaining extended life of the credit facility.
	At the same time, the Company also announced an increase in the maximum borrowing capability of its commercial paper program from $700,000 to $1,000,000.
	AWCC had the following available capacity under its commercial paper program at December 31:

		2014			2013
	Commercial paper program	$	1,000,000		$	1,000,000
	Commercial paper program available capacity		550,000			369,500
	At December 31, AWCC had the following sub-limits and available capacity under each applicable credit facility:

		2014			2013
	Letter of credit sublimit	$	150,000		$	150,000
	Letter of credit available capacity		112,104			108,215
	At December 31, 2014 and 2013, the Company had $37,896 and $41,785 of outstanding letters of credit, respectively, all of which were issued under the revolving credit facility noted above.
	The following table presents the short-term borrowing activity for AWCC for the years ended December 31, 2014 and 2013:

		2014			2013(1)
	Average borrowings	$	548,530		$	370,420
	Maximum borrowings outstanding		745,000			829,250
	Weighted average interest rates, computed on daily basis		0.31	%		0.43	%
	Weighted average interest rates, at Dec 31		0.42	%		0.36	%
	(1) 2013 average borrowings, maximum borrowings outstanding, and weighted average interest rates, computed on daily basis have been revised by immaterial amounts.
	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 at December 31, 2014 was 0.55 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 to successfully argue that no collateral should 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 (General Taxes)	12 Months Ended
General Taxes (General Taxes)	Dec. 31, 2014
General Taxes
General Taxes	Note 11: General Taxes
	Components of general tax expense from continuing operations for the years ended December 31 are as follows:

		2014		2013		2012
	Gross receipts and franchise	$	96,014	$	96,044	$	92,612
	Property and capital stock		95,651		94,394		84,448
	Payroll		30,698		30,985		32,335
	Other general		14,369		12,775		11,363
		$	236,732	$	234,198	$	220,758

Income_Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Note 12: Income Taxes
	Components of income tax expense from continuing operations for the years ended December 31 are as follows:

		2014			2013			2012
	State income taxes
	Current	$	11,055		$	7,202		$	26,604
	Deferred
	Current		(287	)		(405	)		(280	)
	Non-current		30,788			26,821			24,256
		$	41,556		$	33,618		$	50,580

	Federal income taxes
	Current	$	14,767		$	(19,995	)	$	31,482
	Deferred
	Current		(1,528	)		(1,324	)		(2,031	)
	Non-current		226,572			226,295			178,274
	Amortization of deferred investment tax credits		(1,394	)		(1,501	)		(1,518	)
			238,417			203,475			206,207
		$	279,973		$	237,093		$	256,787
	A reconciliation of income tax expense from continuing operations at the statutory federal income tax rate to actual income tax expense for the years ended December 31 is as follows:

		2014			2013			2012
	Income tax at statutory rate	$	248,424		$	212,777		$	220,636
	Increases (decreases) resulting from:
	State taxes, net of federal taxes		27,011			21,852			32,877
	Change in valuation allowance		(2	)		(455	)		143
	Flow through differences		3,467			3,217			3,032
	Amortization of deferred investment tax credits		(1,394	)		(1,501	)		(1,518	)
	Subsidiary preferred dividends		532			584			634
	Sec 162(m) Adjustment		980			—			—
	Other, net		955			619			983
	Actual income tax expense	$	279,973		$	237,093		$	256,787
	The following table provides the components of the net deferred tax liability from continuing operations at December 31:

		2014			2013
	Deferred tax assets:
	Advances and contributions	$	502,069		$	510,122
	Deferred investment tax credits		9,452			10,027
	Other postretirement benefits		104,723			107,773
	Tax losses and credits		197,288			265,640
	Pension benefits		124,985			122,143
	Unamortized debt discount, net		20,249			20,249
	Other		32,159			23,001
			990,925			1,058,955
	Valuation allowance		(10,379	)		(13,555	)
		$	980,546		$	1,045,400
	Deferred tax liabilities:
	Utility plant, principally due to depreciation differences	$	2,676,574		$	2,478,617
	Income taxes recoverable through rates		75,538			81,135
	Deferred business services project expenses		4,584			4,584
	Deferred other postretirement benefits		65,157			65,071
	Deferred pension benefits		121,317			169,336
	Other		71,514			69,632
			3,014,684			2,868,375
		$	(2,034,138	)	$	(1,822,975	)
	At December 31, 2014 and 2013, the Company recorded federal net operating loss (“NOL”) carryforwards of $1,004,705 and $1,182,075, respectively. The 2014 balance includes $14,325 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 evaluated its ability to fully utilize the existing federal NOL carryforwards in light of the RWE divestiture in November 2009. Under Internal Revenue Code (“I.R.C.”) Section 382, an ownership change occurs if there is a greater than fifty percent (50%) change in equity ownership of a company over a three-year period determined by reference to the ownership of persons holding five percent (5%) or more of that company’s equity securities. If a company undergoes an ownership change as defined by I.R.C. Section 382, the company’s ability to utilize its pre-change NOL carryforwards to offset post-change income may be limited.
	The Company believes that the limitation imposed by I.R.C. Section 382 generally should not preclude use of its federal NOL carryforwards, assuming the Company has sufficient taxable income in future carryforward periods to utilize those NOL carryforwards. The Company’s federal NOL carryforwards do not begin expiring until 2028.
	At December 31, 2014 and 2013, the Company had state NOLs of $542,705 and $628,049, 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 expire between 2015 and 2033.
	At December 31, 2014 and 2013, the Company had Canadian NOL carryforwards of $6,498 and $6,323, 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 2015 and 2033.
	The Company had capital loss carryforwards for federal income tax purposes of $3,844 at December 31, 2014 and 2013. 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 2008. 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 $6,348 and $6,241 at December 31, 2014 and 2013, respectively.
	The following table summarizes the changes in the Company’s gross liability, excluding interest and penalties, for unrecognized tax benefits:

Balance at January 1, 2013	$	180,993
Increases in current period tax positions		27,229
Decreases in prior period measurement of tax positions		(30,275	)
Balance at December 31, 2013	$	177,947
Increases in current period tax positions		53,818
Decreases in prior period measurement of tax positions		(36,528	)
Balance at December 31, 2014	$	195,237
The total balance in the table above does not include interest and penalties of $157 and $242 as of December 31, 2014 and 2013, respectively, which is recorded as a component of income tax expense. The majority of the increased tax position is attributable to temporary differences. The increase in 2014 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 at December 31, 2014 and 2013, an unrecognized tax benefit of $9,444 and $7,439, respectively, excluding interest and penalties, would impact the Company’s effective tax rate.
The following table summarizes the changes in the Company’s valuation allowance:

Balance at January 1, 2012	$	21,579
Increases in current period tax positions		—
Decreases in current period tax positions		(2,059	)
Balance at December 31, 2012	$	19,520
Increases in current period tax positions		—
Decreases in current period tax positions		(5,965	)
Balance at December 31, 2013	$	13,555
Increases in current period tax positions		—
Decreases in current period tax positions		(3,176	)
Balance at December 31, 2014	$	10,379
Included in 2013 is a discrete tax benefit totaling $2,979 associated with an entity re-organization within the Company’s Market-Based Operations segment that allowed for the utilization of state net operating loss carryforwards and the release of an associated valuation allowance.

Employee_Benefits

Employee Benefits	12 Months Ended
Employee Benefits	Dec. 31, 2014
Compensation Related Costs [Abstract]
Employee Benefits	Note 13: 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 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 equity and bond funds, 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)
	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 commingled funds including equity and bond funds 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 at December 31, 2014, by asset category, follow:

	Asset Category		Target				Total				Quoted Prices				Significant				Significant				Percentage of Plan
			Allocation								in Active				Observable				Unobservable				Assets at
			2015								Markets for				Inputs				Inputs				December 31, 2014
											Identical Assets				(Level 2)				(Level 3)
											(Level 1)
	Cash			—			$	8,370			$	8,370			$	—			$	—				—
	Equity securities:
	U.S. large cap			24	%			342,081				342,081				—				—				24	%
	U.S. small cap value			8	%			116,503				116,503				—				—				8	%
	International			20	%			274,143				—				274,143				—				19	%
	Fixed income securities:			40	%																			41	%
	U.S. Treasury and government bonds			—				140,057				121,351				18,706				—				—
	Corporate bonds			—				376,939				—				376,939				—				—
	Mortgage-backed securities			—				4,285				—				4,285				—				—
	Long duration bond fund			—				6,555				6,555				—				—				—
	Guaranteed annuity contracts			—				51,517				—				8,987				42,530				—
	Real estate			6	%			84,821				—				—				84,821				6	%
	REITs			2	%			22,889				—				22,889				—				2	%
	Total			100	%		$	1,428,160			$	594,860			$	705,949			$	127,351				100	%
	The following table presents a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3):

		Level 3
	Balance, January 1, 2014	$	43,825
	Actual return on assets		7,053
	Purchases, issuances and settlements, net		76,473
	Balance, December 31, 2014	$	127,351
	The fair values and asset allocations of pension plan assets at December 31, 2013, by asset category, follow:

	Asset Category		Target				Total				Quoted Prices				Significant				Significant				Percentage of Plan
			Allocation								in Active				Observable				Unobservable				Assets at
			2014								Markets for				Inputs				Inputs				December 31, 2013
											Identical Assets				(Level 2)				(Level 3)
											(Level 1)
	Cash			—			$	12,844			$	12,844			$	—			$	—				—
	Equity securities:
	U.S. large cap			24	%			455,068				455,068				—				—				33	%
	U.S. small cap value			8	%			139,571				139,571				—				—				10	%
	International			20	%			295,226				615				294,611				—				21	%
	Fixed income securities:			40	%																			35	%
	U.S. Treasury and government bonds			—				81,200				76,222				4,978				—				—
	Corporate bonds			—				209,500				—				209,500				—				—
	Mortgage-backed securities			—				116,956				—				116,956				—				—
	Long duration bond fund			—				5,177				5,177				—				—				—
	Guaranteed annuity contracts			—				52,772				—				8,947				43,825				—
	Real estate			6	%			—				—				—				—				—
	REITs			2	%			15,307				—				15,307				—				1	%
	Total			100	%		$	1,383,621			$	689,497			$	650,299			$	43,825				100	%
	The following table presents a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3):
	Level 3
Balance, January 1, 2013	$	173,625
Actual return on assets		10,384
Purchases, issuances and settlements, net		(140,184	)
Balance, December 31, 2013	$	43,825

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 at December 31, 2014, by asset category, follow:

Asset Category		Target				Total				Quoted Prices				Significant				Significant				Percentage of Plan
		Allocation								in Active				Observable				Unobservable				Assets at
		2015								Markets for				Inputs				Inputs				December 31, 2014
										Identical Assets				(Level 2)				(Level 3)
										(Level 1)
Bargain VEBA:
Cash			—			$	189			$	189			$	—				—				—
Equity securities:
U.S. large cap			9	%			34,168				34,168				—				—				9	%
U.S. small cap value			—				—				—				—				—				—
International			11	%			40,232				40,232				—				—				10	%
Fixed income securities:			80	%																			81	%
U.S. Treasury securities and government bonds			—				155,087				155,087				—				—				—
Corporate bonds			—				168,317				—				168,317				—				—
Long duration bond fund			—				3,245				3,245				—				—				—
Future and option contracts (a)			—				387				387				—				—				—
Total bargain VEBA			100	%		$	401,625			$	233,308			$	168,317				—				100	%
Non-bargain VEBA:
Cash			—			$	636			$	636			$	—				—				—
Equity securities:
U.S. large cap			21	%			21,966				21,966				—				—				21	%
U.S. small cap value			21	%			21,123				21,122				1				—				21	%
International			28	%			28,611				28,611				—				—				28	%
Fixed income securities:			30	%																			30	%
Core fixed income bond fund			—				30,762				30,762				—				—				—
Total non-bargain VEBA			100	%		$	103,098			$	103,097			$	1				—				100	%
Life VEBA:
Cash			—			$	65			$	65			$	—				—				—
Equity securities:
U.S. large cap			70	%			4,924				4,924				—				—				67	%
Fixed income securities:			30	%																			33	%
Core fixed income bond fund			—				2,336				2,336				—				—				—
Total life VEBA			100	%		$	7,325			$	7,325			$	—				—				100	%
Total			100	%		$	512,048			$	343,730			$	168,318				—				100	%

(a)	Includes cash for margin requirements.
The fair values and asset allocations of postretirement benefit plan assets at December 31, 2013, by asset category, follow:

Asset Category		Target				Total				Quoted Prices				Significant				Significant				Percentage of Plan
		Allocation								in Active				Observable				Unobservable				Assets at
		2014								Markets for				Inputs				Inputs				December 31, 2013
										Identical Assets				(Level 2)				(Level 3)
										(Level 1)
Bargain Veba:
Cash			—			$	689			$	689			$	—				—				—
Equity securities:
U.S. large cap			18	%			72,108				72,108				—				—				19	%
U.S. small cap value			7	%			26,574				26,574				—				—				7	%
International			15	%			55,888				55,888				—				—				15	%
Fixed income securities:			60	%																			59	%
U.S. Treasury securities and government bonds			—				95,010				91,578				3,432				—				—
Corporate bonds			—				117,843				—				117,843				—				—
Long duration bond fund			—				2,043				2,043				—				—				—
Future and option contracts (a)			—				620				620				—				—				—
Total bargain VEBA			100	%		$	370,775			$	249,500			$	121,275				—				100	%
Non-bargain VEBA:
Cash			—			$	3,451			$	3,451			$	—				—				—
Equity securities:
U.S. large cap			21	%			41,430				41,430				—				—				43	%
U.S. small cap value			21	%			—				—				—				—				0	%
International			28	%			27,739				27,739				—				—				29	%
Fixed income securities:			30	%																			28	%
Core fixed income bond fund			—				23,563				23,563				—				—				—
Total non-bargain VEBA			100	%		$	96,183			$	96,183			$	—				—				100	%
Life VEBA:
Cash			—			$	27			$	27			$	—				—				—
Equity securities:
U.S. large cap			70	%			5,527				5,527				—				—				71	%
Fixed income securities:			30	%																			29	%
Core fixed income bond fund			—				2,206				2,206				—				—				—
Total Life VEBA			100	%		$	7,760			$	7,760			$	—				—				100	%
Total			100	%		$	474,718			$	353,443			$	121,275				—				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
	2014				2013				2014				2013
Change in benefit obligation
Benefit obligation at January 1	$	1,494,132			$	1,621,244			$	561,923			$	687,082
Service cost		31,773				37,872				11,058				15,282
Interest cost		76,652				68,096				28,605				28,700
Plan participants' contributions		—				—				2,625				2,514
Actuarial (gain) loss		255,762				(180,688	)			123,342				(148,410	)
Gross benefits paid		(111,863	)			(52,392	)			(26,440	)			(25,263	)
Federal subsidy		—				—				2,159				2,018
Benefit obligation at December 31	$	1,746,456			$	1,494,132			$	703,272			$	561,923

Change in Plan Assets
Fair value of plan assets at January 1	$	1,383,621			$	1,157,697			$	474,718			$	433,260
Actual return on plan assets		116,363				208,821				48,989				36,202
Employer contributions		40,039				69,495				12,156				28,005
Plan participants' contributions		—				—				2,625				2,514
Benefits paid		(111,863	)			(52,392	)			(26,440	)			(25,263	)
Fair value of plan assets at December 31	$	1,428,160			$	1,383,621			$	512,048			$	474,718

Funded status at December 31	$	(318,296	)		$	(110,511	)		$	(191,224	)		$	(87,205	)

Amounts recognized in the balance sheet consist of:
Noncurrent asset	$	—			$	—			$	1,326			$	1,271
Current liability		(1,928	)			(1,969	)			(48	)			(57	)
Noncurrent liability		(316,368	)			(108,542	)			(192,502	)			(88,419	)
Net amount recognized	$	(318,296	)		$	(110,511	)		$	(191,224	)		$	(87,205	)

Benefits paid in 2014 includes $55,579 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
	2014				2013				2014				2013

Net actuarial loss	$	379,743			$	145,376			$	119,566			$	17,632
Prior service cost (credit)		3,694				4,418				(12,330	)			(14,519	)
Net amount recognized	$	383,437			$	149,794			$	107,236			$	3,113
Regulatory assets	$	248,641			$	90,380			$	107,236			$	3,113
Accumulated other comprehensive income		134,796				59,414				—				—
	$	383,437			$	149,794			$	107,236			$	3,113
At December 31, 2014 and 2013, 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
		2014				2013
Projected benefit obligation		$	1,746,000			$	1,494,000
Fair value of plan assets			1,428,000				1,384,000

		Accumulated Benefit
		Obligation Exceeds the
		Fair Value of Plans' Assets
		2014				2013
Accumulated benefit obligation		$	1,616,000			$	43,000
Fair value of plan assets			1,428,000				17,000
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 2015 to the qualified pension plans. The Company plans to contribute to its 2015 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
2015 expected employer contributions
To plan trusts			$	28,000			$	26,500
To plan participants				1,929				104
The Company made 2015 contributions to fund pension benefits and other benefits of $6,100 and $6,632, respectively, through February 2015.
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
2015		$	63,355			$	27,897			$	2,113
2016			69,673				30,672				2,295
2017			75,894				33,518				2,486
2018			82,063				36,502				2,678
2019			88,635				39,172				2,892
2020—2024			528,913				226,602				18,220
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 are as follows:

		Pension Benefits													Other Benefits
		2014				2013				2012					2014				2013				2012
Weighted-average
assumptions used to
determine December 31
benefit obligations
Discount rate			4.24%				5.12%				4.17%					4.24	%			5.1	%			4.16	%
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 2014				7.00% in 2013				7.25% in 2012
															to 5.00% in 2021+				to 5.00% in 2019+				to 5.00% in 2019+

Weighted-average
assumptions used to
determine net periodic cost
Discount rate			5.12%				4.17%				5.02%					5.1	%			4.16	%			5.05	%
Expected return on plan assets			6.91%				7.49%				7.75%					5.87	%			6.99	%			7.41	%
Rate of compensation increase			3.15%				3.19%				3.25%				N/A				N/A				N/A
Medical trend		N/A				N/A				N/A					graded from				graded from				graded from
															7.00% in 2014				7.25% in 2013				7.50% in 2012
															to 5.00% in 2019+				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.
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.
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		$	5,943			$	(4,887	)
Effect on other postretirement benefit obligation		$	105,967			$	(86,179	)

The following table provides the components of net periodic benefit costs for the years ended December 31:

	2014				2013				2012
Components of net periodic pension benefit cost
Service cost	$	31,773			$	37,872			$	34,209
Interest cost		76,652				68,096				70,866
Expected return on plan assets		(94,838	)			(88,429	)			(79,272	)
Amortization of:
Prior service cost (credit)		724				724				723
Actuarial (gain) loss		(131	)			37,170				29,636
Settlement loss		—				—				7,135
Net periodic pension benefit cost	$	14,180			$	55,433			$	63,297

Other changes in plan assets and benefit obligations recognized in other
comprehensive income
Amortization of prior service credit (cost)	$	(166	)		$	(174	)		$	(176	)
Current year actuarial (gain) loss		46,119				(73,472	)			26,425
Amortization of actuarial gain (loss)		31				(8,911	)			(7,301	)
Total recognized in other comprehensive income	$	45,984			$	(82,557	)		$	18,948
Total recognized in net periodic benefit cost and comprehensive income	$	60,164			$	(27,124	)		$	82,245

Components of net periodic other postretirement benefit cost
Service cost	$	11,058			$	15,282			$	14,207
Interest cost		28,605				28,700				31,570
Expected return on plan assets		(27,500	)			(30,285	)			(28,711	)
Amortization of:
Prior service cost (credit)		(81	)			(2,189	)			(1,915	)
Actuarial (gain) loss		(2,189	)			11,128				9,537
Other		—				—				(696	)
Net periodic other postretirement benefit cost	$	9,893			$	22,636			$	23,992
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 2015 are as follows:

	Pension Benefits				Other Benefits
Actuarial (gain) loss	$	25,108			$	5,009
Prior service cost (credit)		754				(2,189	)
Total	$	25,862			$	2,820
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 $7,595 for 2014, $7,926 for 2013 and $7,990 for 2012. All of the Company’s contributions are invested in one or more funds at the direction of the employee.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 14: 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 $217,082 at December 31, 2014.
	The Company’s regulated subsidiaries maintain agreements with other water purveyors for the purchase of water to supplement their water supply. Purchased water expenses were approximately $124,334, $114,471 and $115,426 for the years ended December 31, 2014, 2013 and 2012, respectively. Future annual commitments related to minimum quantities of purchased water having non-cancelable terms in excess of one year at December 31, 2014 are $55,141 in 2015, $50,936 in 2016, $44,175 in 2017, $43,034 in 2018, $43,098 in 2019 and $441,206 thereafter.
	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 services agreements expire between 2051 and 2064 and have remaining performance commitments as measured by estimated remaining contract revenue of $2,543,778 at December 31, 2014. The military contracts are subject to customary termination provisions held by the U.S. Federal Government prior to the agreed upon contract expiration. The Company’s Operations and Maintenance agreements with municipalities and other customers expire between 2015 and 2048 and have remaining performance commitments as measured by estimated remaining contract revenue of $865,803 at December 31, 2014. 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. At December 31, 2014, the Company has accrued approximately $5,000 as probable costs and it is reasonably possible that additional losses could range up to $30,100 for these matters. For certain matters, the Company is unable to estimate possible losses. The Company believes that damages or settlements, if any, recovered by plaintiffs in such claims or actions will not have a material adverse effect on the Company’s results of operations, financial position or cash flows.
	On October 13, 2014, we entered into a settlement agreement with the Utility Workers Union of America (“UWUA”) designed to resolve a dispute between our company and the labor unions representing employees in the Regulated Businesses (“the Unions”). Among other things, the settlement agreement provides for a new 2014-2018 National Benefits Agreement that will be in effect generally until July 31, 2018. In addition, we agreed to make a $10 million lump-sum payment, to be distributed in accordance with procedures set forth in the settlement agreement among eligible employees represented by the Unions and affected by implementation of our last, best and final offer. The majority of the distributions are expected to be used to reimburse employees for medical claims which were incurred during the relevant period and will be funded by the Group Insurance Plan for American Water Works Company, Inc. and Its Designated Subsidiaries and Affiliates – Active Employees VEBA (the “VEBA Trust”), to which we previously have made contributions.
	The Unions approved the settlement agreement on October 30, 2014, and the National Labor Relations Board (the “NLRB”) approved the settlement agreement on October 31, 2014. The NLRB, UWUA and the Company filed a joint stipulation to dismiss the petition for review. The Seventh Circuit voluntarily dismissed all the parties' appeals on December 16, 2014. The NLRB will dismiss the unfair labor practice charge pending on the national benefits dispute when we have complied with the settlement agreement.

Earnings_Per_Common_Share

Earnings Per Common Share	12 Months Ended
Earnings Per Common Share	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings Per Common Share	Note 15: Earnings per Common Share
	Earnings per share is calculated using the two-class method. The two-class method is an earnings allocation formula that determines earnings per share for each class of common stock and participating security. The Company has participating securities related to restricted stock units, granted under the Company’s 2007 Omnibus Equity Compensation Plan, that earn dividend equivalents on an equal basis with common shares. In applying the two-class method, undistributed earnings are allocated to both common shares and participating securities.
	The following is a reconciliation of the Company’s income from continuing operations, loss from discontinued operations and net income and weighted-average common shares outstanding for calculating basic earnings per share:

		Years Ended December 31,
	Basic	2014			2013			2012
	Income from continuing operations	$	429,841		$	370,844		$	373,602
	Loss from discontinued operations, net of tax		(6,733	)		(1,580	)		(15,532	)
	Net income		423,108			369,264			358,070
	Less: Distributed earnings to common shareholders		217,253			150,038			214,541
	Less: Distributed earnings to participating securities		63			60			86
	Undistributed earnings		205,792			219,166			143,443
	Undistributed earnings allocated to common shareholders		205,735			219,082			143,385
	Undistributed earnings allocated to participating securities		57			84			58
	Total income from continuing operations available to	$	429,721		$	370,700		$	373,458
	common shareholders, basic	$	429,721		$	370,700		$	373,458
	Total income available to common shareholders, basic	$	422,988		$	369,120		$	357,926

	Weighted-average common shares outstanding, basic		178,888			177,814			176,445
	Basic earnings per share: (a)
	Income from continuing operations	$	2.4		$	2.08		$	2.12
	Loss from discontinued operations, net of tax	$	(0.04	)	$	(0.01	)	$	(0.09	)
	Net income	$	2.36		$	2.08		$	2.03
	(a)Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.
	Diluted earnings per common share is based on the weighted-average number of common shares outstanding adjusted for the dilutive effect of common stock equivalents related to the restricted stock units, stock options, and employee stock purchase plan. The dilutive effect of the common stock equivalents is calculated using the treasury stock method and expected proceeds on vesting of the restricted stock units, exercise of the stock options and purchases under the employee stock purchase plan.
	The following is a reconciliation of the Company’s income from continuing operations, loss from discontinued operations and net income and weighted-average common shares outstanding for calculating diluted earnings per share:

		Years Ended December 31,
	Diluted	2014			2013			2012
	Total income from continuing operations available to	$	429,721		$	370,700		$	373,458
	common shareholders, basic	$	429,721		$	370,700		$	373,458
	Loss from discontinued operations, net of tax		(6,733	)		(1,580	)		(15,532	)
	Total income available to common shareholders, basic		422,988			369,120			357,926
	Undistributed earnings for participating securities		57			84			58
	Total income from continuing operations available to	$	429,778		$	370,784		$	373,516
	common shareholders, diluted	$	429,778		$	370,784		$	373,516
	Total income available to common shareholders, diluted	$	423,045		$	369,204		$	357,984

	Weighted-average common shares outstanding, basic		178,888			177,814			176,445
	Common stock equivalents:
	Restricted stock units		454			510			618
	Stock options		463			730			607
	Employee stock purchase plan		1			2			1
	Weighted-average common shares outstanding, diluted		179,806			179,056			177,671
	Diluted earnings per share (a)
	Income from continuing operations	$	2.39		$	2.07		$	2.1
	Loss from discontinued operations, net of tax	$	(0.04	)	$	(0.01	)	$	(0.09	)
	Net income	$	2.35		$	2.06		$	2.01
	(a)Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.
	The following potentially dilutive common stock equivalents were not included in the earnings per share calculations for the years ended December 31 because they were anti-dilutive:

		2014			2013			2012
	Stock options		323			327			619
	Restricted stock units where certain performance		—			20			19
	conditions were not met		—			20			19

Fair_Values_of_Financial_Instr

Fair Values of Financial Instruments	12 Months Ended
Fair Values of Financial Instruments	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	Note 16: 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 are as follows:

			Carrying				At Fair Value as of December 31, 2014
			Amount				Level 1				Level 2			Level 3		Total
	Preferred stock with mandatory redemption		$	17,151			$ —				$ —			$	22,167	$	22,167
	requirements		$	17,151			$ —				$ —			$	22,167	$	22,167
	Long-term debt (excluding capital lease			5,491,341				2,874,622				1,474,708			2,055,058		6,404,388
	obligations)			5,491,341				2,874,622				1,474,708			2,055,058		6,404,388

			Carrying				At Fair Value as of December 31, 2013
			Amount				Level 1				Level 2			Level 3		Total
	Preferred stock with mandatory redemption		$	18,827			$ —				$ —			$	22,795	$	22,795
	requirements		$	18,827			$ —				$ —			$	22,795	$	22,795
	Long-term debt (excluding capital lease			5,224,492				2,263,355				1,462,404			2,057,506		5,783,265
	obligations)			5,224,492				2,263,355				1,462,404			2,057,506		5,783,265
	Fair Value Measurements
	To increase consistency and comparability in fair value measurements, FASB guidance 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, 2014 and 2013, respectively:

	Recurring Fair Value Measures				At Fair Value as of December 31, 2014
					Level 1				Level 2				Level 3	Total
	Assets:
	Restricted funds				$	45,182			$ —				$ —	$	45,182
	Rabbi trust investments				—					11,751			—		11,751
	Deposits					4,158			—				—		4,158
	Mark-to-market derivative asset				—					3,636			—		3,636
	Total assets					49,340				15,387			—		64,727

	Liabilities:
	Deferred compensation obligation				—					11,765			—		11,765
	Mark-to-market derivative liability				—					1,012			—		1,012
	Total liabilities				—					12,777			—		12,777
	Total net assets				$	49,340			$	2,610			$ —	$	51,950

	Recurring Fair Value Measures				At Fair Value as of December 31, 2013
					Level 1				Level 2				Level 3	Total
	Assets:
	Restricted funds				$	29,259			$ —				$ —	$	29,259
	Rabbi trust investments				—					444			—		444
	Deposits					1,901			—				—		1,901
	Mark-to-market derivative asset				—					4,776			—		4,776
	Total assets					31,160				5,220			—		36,380

	Liabilities:
	Deferred compensation obligation				—					11,928			—		11,928
	Mark-to-market derivative liability				—					1,276			—		1,276
	Total liabilities				—					13,204			—		13,204
	Total net assets (liabilities)				$	31,160			$	(7,984	)		$ —	$	23,176

	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. Restricted funds expected to be released within twelve months subsequent to year end are classified as current. Also included in the above restricted funds in 2014 is $22,366 of money market funds held in trust for active employee benefits.
	Rabbi trust investments—The Company’s rabbi trust investments consist primarily of fixed income investments and mutual 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.
	See Note 13 for the Company’s fair value of qualified pension and postretirement welfare plans’ assets.
	Non-recurring Fair Value Measurements
As discussed in Note 7, the Company recognized continuing operations goodwill impairment charges of $0 for each of the years ended December 31, 2014, 2013 and 2012, respectively. The Company’s goodwill valuation model includes significant unobservable inputs and falls within Level 3 of the fair value hierarchy.

Leases

Leases	12 Months Ended
Leases	Dec. 31, 2014
Leases [Abstract]
Leases	Note 17: Leases
	The Company has entered into operating leases involving certain facilities and equipment. Rental expenses under operating leases were $21,885 for 2014, $23,351 for 2013 and $27,945 for 2012. The operating leases for facilities will expire over the next 20 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.
	At December 31, 2014, the minimum annual future rental commitment under operating leases that have initial or remaining non-cancelable lease terms in excess of one year are $14,007 in 2015, $11,898 in 2016, $10,970 in 2017, $9,763 in 2018, $9,457 in 2019 and $81,617 thereafter.
	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 $156,819 and $158,115 at December 31, 2014 and 2013, respectively, which is presented within utility plant. The future payments under the lease obligations are equal to and offset by the payments receivable under the IDBs.
	At December 31, 2014, 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 $3,755 in 2015 through 2019, and $73,318 thereafter.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Information	Note 18: Segment Information
	The Company has two operating segments referred to as the Regulated Businesses and Market-Based Operations segments. The Company’s chief operating decision maker regularly reviews the operating results of the Regulated Businesses and Market-Based Operations segments to assess segment performance and allocate resources. The evaluation of segment performance and the allocation of resources are based on several measures. The measure that is most consistent with that used by management is income from continuing operations before income tax.
	The Regulated Businesses segment includes the Company’s 18 utility subsidiaries in continuing operations that provide water and wastewater services to customers in 16 U.S. states. The Market-Based Operations segment is comprised of market-based businesses that provide a broad range of water and wastewater services and products including homeowner water and sewer line maintenance services and water and wastewater facility operations and maintenance services.
	The accounting policies of the segments are the same as those described in the summary of significant accounting policies. (See Note 2) The Regulated Businesses and Market-Based Operations segment information includes intercompany costs that are allocated by American Water Works Service Company, Inc. and intercompany interest that is charged by AWCC, which are eliminated to reconcile to the consolidated results of operations. Inter-segment revenues, which are primarily recorded at cost plus 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 subsidiaries, eliminations of inter-segment transactions, fair value adjustments and associated income and deductions related to the Acquisitions that have not been allocated to the segments for evaluation of segment 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 following table includes the Company’s summarized segment information:

		As of or for the Year Ended
		31-Dec-14
		Regulated Businesses		Market-Based Operations		Other			Consolidated
	Net operating revenues	$	2,674,329	$	354,679	$	(17,680	)	$	3,011,328
	Depreciation and amortization		394,097		5,790		24,197			424,084
	Total operating expenses, net		1,725,651		299,549		(16,448	)		2,008,752
	Income from continuing operations before		707,449		57,539		(55,174	)		709,814
	income taxes
	Total assets		14,342,837		314,253		1,473,866			16,130,956
	Capital expenditures		946,306		9,813	—				956,119
	Capital expenditures of discontinued operations	—			12	—				12
	(included in capital expenditures above)

		As of or for the Year Ended
		31-Dec-13
		Regulated Businesses		Market-Based Operations		Other			Consolidated
	Net operating revenues (1)	$	2,593,918	$	302,541	$	(17,523	)	$	2,878,936
	Depreciation and amortization (1)		375,939		6,012		24,766			406,717
	Total operating expenses, net (1)		1,700,052		252,302		(21,734	)		1,930,620
	Income from continuing operations before		654,834		53,104		(100,001	)		607,937
	income taxes (1)
	Total assets		13,447,696		286,048		1,354,398			15,088,142
	Assets of discontinued operations (included	—			7,761	—				7,761
	in total assets above)
	Capital expenditures		973,301		6,951	—				980,252
	Capital expenditures of discontinued operations	—			517	—				517
	(included in capital expenditures above)

		As of or for the Year Ended
		31-Dec-12
		Regulated Businesses		Market-Based Operations		Other			Consolidated
	Net operating revenues (1)	$	2,564,434	$	307,366	$	(17,874	)	$	2,853,926
	Depreciation and amortization (1)		349,629		5,560		25,213			380,402
	Total operating expenses, net (1)		1,685,734		266,005		(21,917	)		1,929,822
	Income from continuing operations before		649,117		44,948		(63,676	)		630,389
	income taxes (1)
	Total assets		12,680,856		260,255		1,777,865			14,718,976
	Assets of discontinued operations (included	—			7,646	—				7,646
	in total assets above)
	Capital expenditures		921,500		7,074	—				928,574
	Capital expenditures of discontinued operations		2,884		705	—				3,589
	(included in capital expenditures above)

	(1) The information has been restated to reflect the impact of discontinued operations, as applicable. See Note 3 for additional details on the Company’s discontinued operations.

Unaudited_Quarterly_Data

Unaudited Quarterly Data	12 Months Ended
Unaudited Quarterly Data	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Unaudited Quarterly Data	Note 19: Unaudited Quarterly Data
	The following table sets forth certain supplemental unaudited consolidated quarterly financial data for each of the four quarters in the years ended December 31, 2014 and 2013, respectively. The operating results for any quarter are not indicative of results that may be expected for a full year or any future periods:

	2014	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
		(In thousands, except per share data)
	Net operating revenues	$	679,003	$	754,778	$	846,169	$	731,378
	Operating income		187,442		254,788		337,285		223,061
	Income from continuing operations		69,113		110,174		156,608		93,946
	Net income		68,123		109,299		152,185		93,501
	Basic earnings per common share:
	Income from continuing operations		0.39		0.62		0.87		0.52
	Net income		0.38		0.61		0.85		0.52
	Diluted earnings per common share:
	Income from continuing operations		0.39		0.61		0.87		0.52
	Net income		0.38		0.61		0.85		0.52

	2013	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
		(In thousands, except per share data)
	Net operating revenues	$	631,939	$	718,565	$	822,190	$	706,242
	Operating income		165,324		242,031		323,166		217,795
	Income from continuing operations		58,445		101,369		149,909		61,121
	Net income		57,643		101,263		150,665		59,693
	Basic earnings per common share:
	Income from continuing operations		0.33		0.57		0.84		0.34
	Net income		0.32		0.57		0.85		0.33
	Diluted earnings per common share:
	Income from continuing operations		0.33		0.57		0.84		0.34
	Net income		0.32		0.57		0.84		0.33

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Dec. 31, 2014
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation
Principles of Consolidation	The accompanying consolidated financial statements include the accounts of AWW and its subsidiaries. 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 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 earnings as earnings or losses of investee.
Use of Estimates	Use of Estimates
Use of Estimates	The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States 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 benefit plan assumptions; the estimates used in impairment testing of goodwill and other long-lived assets, including regulatory assets; revenue recognition; and accounting for income taxes to be its critical accounting estimates. The Company’s significant accounting estimates that are particularly sensitive to change in the near term are amounts reported for pension and other postemployment benefits, contingency-related obligations and goodwill.
Regulation	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 have allowed recovery of costs and credits which the Company has recorded as regulatory assets and liabilities. Accounting for future recovery of costs and credits as regulatory assets and liabilities is in accordance with authoritative guidance applicable to those companies whose rates are established by or are subject to approval by an independent third-party PUC. Regulated utilities defer costs and credits on the balance sheet as regulatory assets and liabilities when it is probable that those costs and credits will be recognized in the rate making process in a period different from the period in which they would have been reflected in operations by a market-based company. These deferred regulatory assets and liabilities are then reflected in the statement of operations in the period in which the costs and credits are reflected in the rates charged for service. (See Note 6)
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. 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 $319,517 and $303,798 at December 31, 2014 and 2013, respectively.
	When units of property are replaced, retired or abandoned, the recorded value thereof 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.
	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 estimated useful lives of the assets, ranging from three to 50 years.
Cash and Cash Equivalents	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	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 of these financings are held in escrow until the designated expenditures are incurred. Classification of restricted funds in the balance sheet as either current or long-term is based upon the intended use of the funds.
Accounts Receivable	Accounts and Unbilled Receivables
Accounts Receivable	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 receivables are accrued when service has been provided but has not been billed to customers.
Allowance for Uncollectible Accounts	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 writes off accounts when they become uncollectible. (See Note 5)
Materials and Supplies	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. A provision is made to reduce excess or obsolete inventory to its net realizable value.
Goodwill	Goodwill
	Goodwill is primarily associated with the acquisitions of AWW in 2003 and E’town Corporation in 2001 (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 Operations segment is comprised of three reporting units. Goodwill is tested annually or more frequently if changes in circumstances indicate goodwill may be impaired. Impairment exists when the carrying value of a reporting unit exceeds its fair value. Annual impairment tests are performed in the fourth quarter of the calendar year, in conjunction with the timing of the completion of the Company’s annual strategic business plan.
	The Company considers the carrying value of goodwill to be one of its critical accounting estimates. 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 considers the estimates used in the determination of fair value of long-lived assets to be one of its critical accounting estimates. 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.
	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 (“advances”) and contributions in aid of construction (“contributions”) 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 at December 31, 2014 and 2013 in the accompanying Consolidated Balance Sheets are estimated refunds of $18,366 and $17,308, 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 subsidiaries do not amortize contributions, and any contribution received remains on the balance sheet indefinitely. Amortization of contributions in aid of construction was $23,913, $22,363 and $20,979 for the years ended December 31, 2014, 2013 and 2012, 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 invoice to the end of the accounting period.
	The Company has agreements with the United States Government 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 operations and management components. The military agreements are subject to periodic price redetermination adjustments and modifications for changes in circumstance. Additionally, the Company has agreements ranging in length from two to 40 years with various industries and municipalities 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 14)
Construction Contracts	Construction Contracts
Construction Contracts	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
	AWW 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")	Allowance for Funds Used During Construction (“AFUDC”)
Allowance for Funds Used During Construction ("AFUDC")	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.
Environmental Costs	Environmental Costs
Environmental Costs	The Company’s water and wastewater operations are subject to 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 $2,200 and $3,300 at December 31, 2014 and 2013, 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 $1,100 annually from 2010 to 2016. The Company pursues recovery of incurred costs through all appropriate means, including regulatory recovery through customer rates. The Company’s regulatory assets at December 31, 2014 and 2013 include $7,791 and $8,027, respectively, related to the NOAA agreement.
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.
New Accounting Standards	New Accounting Standards
	The following recently issued accounting standards have been adopted by the Company and have been included in the consolidated results of operations, financial position or footnotes of the accompanying Consolidated Financial Statements:
	Obligations Resulting from Joint and Several Liability Arrangements
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued guidance for the recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. Examples of obligations within the scope of the updated guidance include debt arrangements, other contractual obligations and settled litigation and judicial rulings. The update requires an entity to measure obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of the following: (a) the amount the reporting entity agreed to pay on the basis of its arrangement among its co-obligors and (b) any additional amount the reporting entity expects to pay on behalf of its co-obligors. The updated guidance also includes additional disclosures regarding the nature and amount of the obligation, as well as other information about those obligations. The update was effective on a retrospective basis for interim and annual periods beginning after December 15, 2013, which for the Company was January 1, 2014. The adoption of this updated guidance did not have an impact on the Company’s results of operations, financial position or cash flows.
	Foreign Currency Matters
	In June 2013, the FASB issued guidance for a parent’s accounting for the cumulative translation adjustment upon derecognition of certain subsidiaries or groups of assets within a foreign entity or of an investment in a foreign entity. The amendments resolve differing views in practice and apply to the release of the cumulative translation adjustment into net income when a parent either sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or a business within a foreign entity. The update was effective prospectively for interim and annual periods beginning after December 15, 2013, which for the Company was January 1, 2014. The adoption of this updated guidance did not have an impact on the Company’s results of operations, financial position or cash flows.
	The following recently issued accounting standards are not yet required to be adopted by the Company:
	Service Concession Arrangements
	In January 2014, the FASB issued guidance for an operating entity that enters into a service concession arrangement with a public sector grantor who controls or has the ability to modify or approve the services that the operating entity must provide with the infrastructure, to whom it must provide the services and at what price. The grantor also controls, through ownership or otherwise, any residual interest in the infrastructure at the end of the term of the arrangement. The guidance specifies that an operating entity should not account for the service concession arrangement as a lease. The operating entity should refer instead to other accounting guidance to account for the various aspects of the arrangement. The guidance also specifies that the infrastructure used in the arrangement should not be recognized as property, plant and equipment of the operating entity. This update should be applied on a modified retrospective basis to service concession arrangements that exist at the beginning of an entity’s fiscal year of adoption. This requires the cumulative effect of applying the update to be recognized as an adjustment to the opening retained earnings balance for the annual period of adoption. The update is effective for interim and annual periods beginning after December 15, 2014, which for the Company is January 1, 2015. The adoption of this updated guidance resulted in a decrease to nonutility property and opening retained earnings of approximately $12,000 on January 1, 2015.
	Reporting Discontinued Operations
	In April 2014, the FASB issued guidance that changes the criteria for determining which disposals can be presented as discontinued operations and modifies related disclosure requirements. Under the updated guidance, 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. A strategic shift could include a disposal of a major geographical area of operations, a major line of business, a major equity method investment or other major part of the entity. A component comprises operations and cash flows that can be clearly distinguished, operationally and for financial reporting purposes, from the rest of the entity including a reportable segment, an operating segment, a reporting unit, a subsidiary or an asset group. 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. The updated guidance is effective on a prospective basis for interim and annual periods on or after December 15, 2014, which for the Company is January 1, 2015. In general, this guidance is likely to result in fewer disposals of assets qualifying as discontinued operations, but will ultimately be based on the Company’s future disposal activity.
	Revenue from Contracts with Customers
	In May 2014, the FASB issued a comprehensive new revenue recognition standard that supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the new guidance is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance is effective for annual and interim periods beginning December 15, 2016, which for the Company is January 1, 2017. Early adoption is not permitted. The new guidance allows for either full retrospective adoption, meaning the guidance is applied to all of the periods presented, or modified retrospective adoption, meaning the standard is applied only to the most current period presented in the financial statements. The Company is evaluating the new guidance, the best transition method and the impact the new standard will have on its results of operations, financial position or cash flows.
	Accounting for Stock-based Compensation with Performance Targets
	In June 2014, the FASB issued guidance for the accounting for stock-based compensation tied to performance targets. The amendments clarify that a performance target that affects vesting of a share-based payment and that could be achieved after the requisite service period is a performance condition. As a result, the target is not reflected in the estimation of the award’s grant date fair value and compensation cost would be recognized over the required service period, if it is probable that the performance condition will be achieved. The updated guidance may be applied either: (a) prospectively to all awards granted or modified after the effective date or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. The updated guidance is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, which for the Company is January 1, 2016. Early adoption is permitted. The Company is evaluating the impact the updated guidance will have on its results of operations, financial position or cash flows.
	Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern
	In August 2014, the FASB issued guidance that explicitly requires an entity’s management to assess the entity’s ability to continue as a going concern. The new guidance requires an entity to evaluate, at each interim and annual period, whether there are conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date the financial statements are issued (or are available to be issued) and to provide related disclosures, if applicable. The new guidance is effective for annual periods ending after December 15, 2016 and for interim and annual periods thereafter, which for the Company is January 1, 2017. Early adoption is permitted. The adoption of this updated guidance is not expected to have a material impact on results of operations, financial position or cash flows.
	Hybrid Financial Instruments Issued in the Form of a Share
	In November 2014, the FASB updated the derivatives and hedging guidance requiring issuers of, or investors in, hybrid financial instruments to determine whether the nature of the host contract is more akin to a debt instrument or an equity instrument by considering the economic characteristics and risks of the entire hybrid financial instrument, including the embedded derivative feature that is being evaluated for separate accounting from the host contract. This update should be applied on a modified retrospective basis to hybrid financial instruments issued in the form of a share that exist at the beginning of an entity’s fiscal year of adoption. The updated guidance is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, which for the Company is January 1, 2016. Early adoption is permitted. The Company is evaluating the impact the updated guidance will have on its results of operations, financial position or cash flows.
	Extraordinary and Unusual Items
	In January 2015, the FASB issued guidance that eliminates the concept of an extraordinary item. As a result, an entity will no longer segregate an extraordinary item and present it separately from the results of ordinary operations or separately disclose income taxes or earnings per share information applicable to an extraordinary item. The presentation and disclosure guidance for items that are unusual in nature or occur infrequently has been retained and expanded to include items that are both unusual in nature and infrequently occurring. The updated guidance is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, which for the Company is January 1, 2016. Early adoption is permitted. The updated guidance may be applied prospectively or retrospectively to all periods presented in the financial statements. The adoption of this updated guidance is not expected to have a material impact on results of operations, financial position or cash flows.
	Reclassifications
	In 2014 the Company reclassified previously reported data to conform to the current presentation for discontinued operations. See Note 3 for additional details on the Company’s discontinued operations.
	In 2014 the Company revised its 2013 balance sheet to properly reclassify $17,722 of deferred income taxes from current liabilities to current assets. This reclassification was not material to the previously issued financial statements.

Acquisitions_and_Divestitures_

Acquisitions and Divestitures (Tables)	12 Months Ended
Acquisitions and Divestitures (Tables)	Dec. 31, 2014
Business Combinations [Abstract]
Summary of Discontinued Operations Presented in Consolidated Statements of Operations, Comprehensive Income	A summary of discontinued operations presented in the Consolidated Statements of Operations and Comprehensive Income follows:

		Years Ended December 31,
		2014			2013			2012
	Operating revenues	$	13,614		$	22,922		$	42,341
	Total operating expenses, net		19,482			25,389			49,726
	Operating loss		(5,868	)		(2,467	)		(7,385	)
	Other income (expenses), net	—			—				(167	)
	Income (loss) from discontinued operations before		(5,868	)		(2,467	)		(7,552	)
	income taxes		(5,868	)		(2,467	)		(7,552	)
	Provision (benefit) for income taxes		865			(887	)		7,980
	Income (loss) from discontinued operations	$	(6,733	)	$	(1,580	)	$	(15,532	)

Summary of Reclassified Assets Discontinued Operations Held For Sale and Liabilities Discontinued Operations Held For Sale	Assets and liabilities of discontinued operations at December 31, 2013 relate to the discontinued Terratec business that was sold in November 2014. The classification for the year ended December 31, 2013 was as follows:

			2013
	ASSETS
	Total property, plant and equipment		$	2,808
	Current assets			4,953
	Total assets of discontinued operations		$	7,761

	LIABILITIES
	Current liabilities		$	3,824
	Total liabilities of discontinued operations		$	3,824

Utility_Plant_Tables

Utility Plant (Tables)	12 Months Ended
Utility Plant (Tables)	Dec. 31, 2014
Disclosure Components Of Utility Plant By Category [Abstract]
Schedule of Major Classes of Utility Plant by Category	The major classes of utility plant by category at December 31 are as follows:

		Range of Remaining
		Useful Lives	2014		2013
	Water plant
	Land and other non-depreciable assets		$	137,199	$	132,295
	Sources of supply	11 to 127 Years		680,623		659,249
	Treatment and pumping facilities	3 to 101 Years		2,969,411		3,006,140
	Transmission and distribution facilities	9 to 156 Years		7,962,759		7,489,208
	Services, meters and fire hydrants	9 to 122 Years		3,062,568		2,898,293
	General structures and equipment	1 to 154 Years		1,035,857		995,186
	Wastewater plant	2 to 115 Years		739,963		683,112
	Construction work in progress			303,004		275,202
				16,891,384		16,138,685
	Less accumulated depreciation			3,991,680		3,894,326
			$	12,899,704	$	12,244,359

Allowance_for_Uncollectible_Ac1

Allowance for Uncollectible Accounts (Tables)	12 Months Ended
Allowance for Uncollectible Accounts (Tables)	Dec. 31, 2014
Disclosure Schedule Of Allowances For Uncollectible Accounts [Abstract]
Schedule of Allowances for Uncollectible Accounts	The following table summarizes the changes in the Company’s allowances for uncollectible accounts:

		2014			2013			2012

	Balance at January 1	$	(33,823	)	$	(26,744	)	$	(18,902	)
	Amounts charged to expense		(36,717	)		(26,953	)		(26,701	)
	Amounts written off		42,886			23,914			22,607
	Recoveries of amounts written off		(7,287	)		(4,040	)		(3,748	)
	Balance at December 31	$	(34,941	)	$	(33,823	)	$	(26,744	)

Regulatory_Assets_and_Liabilit1

Regulatory Assets and Liabilities (Tables)	12 Months Ended
Regulatory Assets and Liabilities (Tables)	Dec. 31, 2014
Disclosure Regulatory Assets And Liabilities Additional Information [Abstract]
Components of Regulatory Assets	The regulatory assets represent costs that are expected to be fully recovered from customers in future rates. Except for income taxes, regulatory assets are excluded from the Company’s rate base and generally do not earn a return. The components of regulatory assets at December 31 are as follows:

		2014		2013
	Income taxes recoverable through rates	$	228,601	$	242,902
	Debt and preferred stock expense		71,403		72,349
	Deferred pension expense		263,486		109,799
	Deferred other postretirement benefit expense		106,792		3,653
	Deferred business services project expense		7,530		7,763
	Deferred tank painting costs		37,207		33,519
	Deferred rate case expense		6,785		9,407
	Purchase premium recoverable through rates		60,412		60,787
	Environmental remediation recoverable through rates		7,791		8,027
	Coastal water project costs		8,386		16,826
	San Clemente Dam project costs		71,891		44,404
	Removal costs recoverable through rates		163,123		126,771
	Regulatory balancing accounts		60,043		63,083
	Other		59,979		59,175
		$	1,153,429	$	858,465

Components of Regulatory Liabilities	The components of regulatory liabilities at December 31 are as follows:

		2014		2013

	Removal costs recovered through rates	$	300,635	$	301,537
	Pension and other postretirement benefit		53,734		40,837
	balancing accounts		53,734		40,837
	Other		37,413		30,945
		$	391,782	$	373,319

Goodwill_Tables

Goodwill (Tables)	12 Months Ended
Goodwill (Tables)	Dec. 31, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Changes in Goodwill Assets	The changes in the Company’s carrying value of goodwill by reporting unit are as follows:

		Regulated Unit						Market-Based Operations					Consolidated
		Cost			Accumulated Impairment			Cost		Accumulated Impairment			Cost			Accumulated Impairment			Total Net
	Balance at January 1, 2013	$	3,411,549		$	(2,332,670	)	$	235,990	$	(107,619	)	$	3,647,539		$	(2,440,289	)	$	1,207,250
	Goodwill from acquisitions		428			—			—		—			428			—			428
	Reclassifications and other		86			—			—		—			86			—			86
	activity		86			—			—		—			86			—			86
	Balance at December 31, 2013	$	3,412,063		$	(2,332,670	)	$	235,990	$	(107,619	)	$	3,648,053		$	(2,440,289	)	$	1,207,764

	Goodwill from acquisitions		354			—			—		—			354			—			354
	Reclassifications and other		(75	)		—			—		—			(75	)		—			(75	)
	activity		(75	)		—			—		—			(75	)		—			(75	)
	Balance at December 31, 2014	$	3,412,342		$	(2,332,670	)	$	235,990	$	(107,619	)	$	3,648,332		$	(2,440,289	)	$	1,208,043

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	12 Months Ended
Stockholders' Equity (Tables)	Dec. 31, 2014
Summary Information Regarding Issuances Under DRIP	The following table summarizes information regarding issuances under the DRIP for the years ended December 31, 2014 and 2013:

		2014			2013
	Shares of common stock issued		44			53
	Cash proceeds received	$	2,119		$	2,171

Cash Dividend Payment During Period	Cash dividend payments made during 2014 and 2013 were as follows:

		2014			2013
	Dividends per share, three months ended:
	31-Mar	$	0.28		$	—
	30-Jun		0.31			0.28
	30-Sep		0.31			0.28
	31-Dec		0.31			0.28

	Total dividends paid, three months ended:
	31-Mar	$	49,968		$	—
	30-Jun		55,422			49,744
	30-Sep		55,458			49,810
	31-Dec		55,506			49,896

Schedule of Accumulated Other Comprehensive Loss	The following table presents changes in accumulated other comprehensive loss by component, net of tax:

		Defined Benefit Plans
		Employee Benefit Plan Funded Status			Amortization of Prior Service Cost			Amortization of Actuarial (Gain) Loss			Foreign Currency Translation			Loss on Cash Flow Hedge			Total Accumulated Other Comprehensive Loss
	Beginning balance at January 1, 2013	$	(143,183	)	$	539		$	22,239		$	4,214		$	—		$	(116,191	)
	Other comprehensive income (loss) before		73,472			—			—			(1,001	)		—			72,471
	reclassifications		73,472			—			—			(1,001	)		—			72,471
	Amounts reclassified from accumulated		—			174			8,911			—			—			9,085
	other comprehensive income (loss)		—			174			8,911			—			—			9,085
	Net comprehensive income (loss) for the		73,472			174			8,911			(1,001	)		—			81,556
	period		73,472			174			8,911			(1,001	)		—			81,556
	Ending balance at December 31, 2013	$	(69,711	)	$	713		$	31,150		$	3,213		$	—		$	(34,635	)
	Other comprehensive income (loss) before		(46,119	)		—			—			(458	)		(820	)		(47,397	)
	reclassifications		(46,119	)		—			—			(458	)		(820	)		(47,397	)
	Amounts reclassified from accumulated		—			166			(31	)		—			29			164
	other comprehensive income (loss)		—			166			(31	)		—			29			164
	Net comprehensive income (loss) for the		(46,119	)		166			(31	)		(458	)		(791	)		(47,233	)
	period		(46,119	)		166			(31	)		(458	)		(791	)		(47,233	)
	Ending balance at December 31, 2014	$	(115,830	)	$	879		$	31,119		$	2,755		$	(791	)	$	(81,868	)

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 and Comprehensive Income for the years ended December 31, 2014, 2013 and 2012:

		2014			2013			2012
	Stock options	$	2,602		$	3,170		$	3,282
	Restricted stock units		9,848			8,718			7,658
	Employee stock purchase plan		593			586			530
	Stock-based compensation in operation and		13,043			12,474			11,470
	maintenance expense		13,043			12,474			11,470
	Income tax benefit		(5,087	)		(4,865	)		(4,473	)
	After-tax stock-based compensation expense	$	7,956		$	7,609		$	6,997

Weighted Average Assumptions	The following table presents 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 in the years ended December 31, 2014, 2013 and 2012:

		2014			2013			2012
	Dividend yield		2.55	%		2.52	%		2.7	%
	Expected volatility		17.75	%		23.5	%		28.35	%
	Risk-free interest rate		1.06	%		0.7	%		0.78	%
	Expected life (years)		3.6			4.3			4.4
	Exercise price	$	44.29		$	39.6		$	34.14
	Grant date fair value per share	$	4.57		$	5.78		$	6.11

Summary of Stock Option Activity	The table below summarizes stock option activity for the year ended December 31, 2014:

		Shares			Weighted-Average Exercise Price (per share)			Weighted-Average Remaining Life (years)			Aggregate Intrinsic Value
	Options outstanding at January 1, 2014		2,055		$	28.8
	Granted		491			44.29
	Forfeited or expired		(62	)		39.23
	Exercised		(574	)		25.4
	Options outstanding at December 31, 2014		1,910		$	33.47			3.9		$	37,881
	Exercisable at December 31, 2014		1,094		$	27.68			2.8		$	28,022

Weighted-Average Assumptions Used In Monte Carlo Simulation	The following table presents the weighted-average assumptions used in the Monte Carlo simulation and the weighted-average grant date fair values of restricted stock units granted during the years ended December 31, 2014, 2013 and 2012:

		2014			2013			2012
	Expected volatility		17.78	%		19.37	%		22.47	%
	Risk-free interest rate		0.75	%		0.4	%		0.43	%
	Expected life (years)		3			3			3
	Grant date fair value per share	$	45.45		$	40.13		$	37.4

Summary of Restricted Stock Unit Activity	The table below summarizes restricted stock unit activity for the year ended December 31, 2014:

		Shares			Weighted-Average Grant Date Fair Value (per share)
	Non-vested total at January 1, 2014		539		$	36.27
	Granted		228			45.45
	Performance share adjustment		113			30.34
	Vested		(337	)		32.13
	Forfeited		(27	)		41.61
	Non-vested total at December 31, 2014		516		$	41.46

Stock Options
Additional Information to Stock Options Activity	The following table summarizes additional information regarding stock options exercised during the years ended December 31, 2014, 2013 and 2012:

		2014			2013			2012
	Intrinsic value	$	12,689		$	15,102		$	14,515
	Exercise proceeds		14,582			20,211			22,112
	Income tax benefit		3,885			4,383			4,017

Restricted Stock Units
Additional Information to Stock Options Activity	The following table summarizes additional information regarding restricted stock units distributed during the years ended December 31, 2014, 2013 and 2012:

		2014			2013			2012
	Intrinsic value	$	15,539		$	13,983		$	6,159
	Income tax benefit		1,625			2,049			799

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2014
Debt Disclosure [Abstract]
Components of Long-Term Debt	The Company primarily incurs long-term debt to fund capital expenditures of the regulated subsidiaries. The components of long-term at December 31 are:

		Rate				Weighted Average Rate				Maturity			2014		2013

	Long-term debt of American Water Capital Corp.
	("AWCC") (a)
	Private activity bonds and government funded
	debt
	Fixed rate	1.79%-6.25%					5.33%			2021-2040		$	231,330	$	330,732
	Senior notes
	Fixed rate	3.40%-8.27%					5.43%			2016-2042			3,753,200		3,312,761
	Long-term debt of other subsidiaries
	Private activity bonds and government funded
	debt
	Fixed rate (b)	0.00%-6.20%					4.73%			2015-2041			795,472		863,716
	Mortgage bonds
	Fixed rate	4.29%-9.71%					7.41%			2015-2039			676,500		676,500
	Mandatorily redeemable preferred stock	8.47%-9.75%					8.60%			2019-2036			17,252		18,902
	Capital lease obligations		12.17%				12.17%			2026			885		913
	Long-term debt												5,474,639		5,203,524
	Unamortized debt, net (c)												31,168		35,984
	Interest rate swap fair value adjustment												3,570		4,724
	Total long-term debt											$	5,509,377	$	5,244,232


	(a)	AWCC, which is a wholly-owned subsidiary of the Company, has a strong support agreement with its parent that, under certain circumstances, is the functional equivalent of a guarantee.
	(b)	Includes $10,190 and $11,920 of variable rate debt with variable-to-fixed interest rate swaps ranging between 3.93% and 4.72%, at December 31, 2014 and 2013, 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 are as follows:


	Year		Amount
	2015		$	61,132
	2016			53,353
	2017			572,775
	2018			455,861
	2019			164,909
	Thereafter			4,166,609

Long-Term Debt Issued	The following long-term debt was issued in 2014:

	Company		Type		Rate		Maturity		Amount
	AWCC		Senior notes—fixed rate		3.40%-4.30%		2025-2042		$	500,000
	Other subsidiaries (1)		Private activity bonds and government funded debt—fixed rate		0.00%-5.00%		2031-2033			10,474
	Total issuances								$	510,474


	-1	Included in the issuance amounts for other subsidiaries private activity bonds and government funded debt above was $9,977, which was initially kept in Trust pending the Company’s certification that it has incurred qualifying capital expenditures. These issuances have been presented as non-cash in the accompanying Consolidated Statements of Cash Flows. Subsequent releases of all or a lesser portion of these funds by the applicable Trust are reflected as the release of restricted funds and are included in investing activities in the accompanying Consolidated Statements of Cash Flows.
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 2014:

	Company		Type		Rate				Maturity		Amount
	AWCC		Private activity bonds and government		6.00%-6.75%				2018-2032		$	101,085
	AWCC		funded debt—fixed rate		6.00%-6.75%				2018-2032		$	101,085
	AWCC		Senior notes—fixed rate			6.00%			2039			59,561
	Other subsidiaries (1)		Private activity bonds and government		0.00%-5.25%				2014-2041			78,718
	Other subsidiaries (1)		funded debt—fixed rate		0.00%-5.25%				2014-2041			78,718
	Other subsidiaries		Mandatorily redeemable preferred stock		8.49%-9.18%				2031-2036			1,650
	Other subsidiaries		Capital lease payments									28
	Total retirements and redemptions										$	241,042


	-1	Includes $1,021 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, 2014 and 2013, and the line items in the Consolidated Balance Sheets in which such amounts are recorded:

	Balance sheet classification		2014				2013
	Regulatory and other long-term assets
	Other		$	3,636			$	4,776
	Long-term debt
	Long-term debt			3,570				4,724

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 as follows:


	Income statement classification		2014				2013				2012
	Interest, net
	Gain (loss) on swap		$	(1,140	)		$	(3,133	)		$	2,085
	Gain (loss) on borrowing			1,154				2,991				(1,604	)
	Hedge ineffectiveness			14				(142	)			481

ShortTerm_Debt_Tables

Short-Term Debt (Tables)	12 Months Ended
Short-Term Debt (Tables)	Dec. 31, 2014
Short Term Borrowings [Abstract]
Schedule of Available Capacity under Commercial Paper Program	AWCC had the following available capacity under its commercial paper program at December 31:

		2014			2013
	Commercial paper program	$	1,000,000		$	1,000,000
	Commercial paper program available capacity		550,000			369,500

Schedule of Line of Credit Facility Sub-Limits and Available Capacity	At December 31, AWCC had the following sub-limits and available capacity under each applicable credit facility:

		2014			2013
	Letter of credit sublimit	$	150,000		$	150,000
	Letter of credit available capacity		112,104			108,215

Schedule Of Short-Term Borrowings Activity	The following table presents the short-term borrowing activity for AWCC for the years ended December 31, 2014 and 2013:

		2014			2013(1)
	Average borrowings	$	548,530		$	370,420
	Maximum borrowings outstanding		745,000			829,250
	Weighted average interest rates, computed on daily basis		0.31	%		0.43	%
	Weighted average interest rates, at Dec 31		0.42	%		0.36	%
	(1) 2013 average borrowings, maximum borrowings outstanding, and weighted average interest rates, computed on daily basis have been revised by immaterial amounts.

General_Taxes_Tables

General Taxes (Tables) (General Tax)	12 Months Ended
General Taxes (Tables) (General Tax)	Dec. 31, 2014
General Tax
Components of General Tax Expense from Continuing Operations	Components of general tax expense from continuing operations for the years ended December 31 are as follows:

		2014		2013		2012
	Gross receipts and franchise	$	96,014	$	96,044	$	92,612
	Property and capital stock		95,651		94,394		84,448
	Payroll		30,698		30,985		32,335
	Other general		14,369		12,775		11,363
		$	236,732	$	234,198	$	220,758

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Components of Income Tax Expense from Continuing Operations	Components of income tax expense from continuing operations for the years ended December 31 are as follows:

		2014			2013			2012
	State income taxes
	Current	$	11,055		$	7,202		$	26,604
	Deferred
	Current		(287	)		(405	)		(280	)
	Non-current		30,788			26,821			24,256
		$	41,556		$	33,618		$	50,580

	Federal income taxes
	Current	$	14,767		$	(19,995	)	$	31,482
	Deferred
	Current		(1,528	)		(1,324	)		(2,031	)
	Non-current		226,572			226,295			178,274
	Amortization of deferred investment tax credits		(1,394	)		(1,501	)		(1,518	)
			238,417			203,475			206,207
		$	279,973		$	237,093		$	256,787

Reconciliation of Income Tax Expense from Continuing Operations	A reconciliation of income tax expense from continuing operations at the statutory federal income tax rate to actual income tax expense for the years ended December 31 is as follows:

		2014			2013			2012
	Income tax at statutory rate	$	248,424		$	212,777		$	220,636
	Increases (decreases) resulting from:
	State taxes, net of federal taxes		27,011			21,852			32,877
	Change in valuation allowance		(2	)		(455	)		143
	Flow through differences		3,467			3,217			3,032
	Amortization of deferred investment tax credits		(1,394	)		(1,501	)		(1,518	)
	Subsidiary preferred dividends		532			584			634
	Sec 162(m) Adjustment		980			—			—
	Other, net		955			619			983
	Actual income tax expense	$	279,973		$	237,093		$	256,787

Components of Net Deferred Tax Liability from Continuing Operations	The following table provides the components of the net deferred tax liability from continuing operations at December 31:

		2014			2013
	Deferred tax assets:
	Advances and contributions	$	502,069		$	510,122
	Deferred investment tax credits		9,452			10,027
	Other postretirement benefits		104,723			107,773
	Tax losses and credits		197,288			265,640
	Pension benefits		124,985			122,143
	Unamortized debt discount, net		20,249			20,249
	Other		32,159			23,001
			990,925			1,058,955
	Valuation allowance		(10,379	)		(13,555	)
		$	980,546		$	1,045,400
	Deferred tax liabilities:
	Utility plant, principally due to depreciation differences	$	2,676,574		$	2,478,617
	Income taxes recoverable through rates		75,538			81,135
	Deferred business services project expenses		4,584			4,584
	Deferred other postretirement benefits		65,157			65,071
	Deferred pension benefits		121,317			169,336
	Other		71,514			69,632
			3,014,684			2,868,375
		$	(2,034,138	)	$	(1,822,975	)

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 at January 1, 2013	$	180,993
	Increases in current period tax positions		27,229
	Decreases in prior period measurement of tax positions		(30,275	)
	Balance at December 31, 2013	$	177,947
	Increases in current period tax positions		53,818
	Decreases in prior period measurement of tax positions		(36,528	)
	Balance at December 31, 2014	$	195,237

Changes in Valuation Allowance	The following table summarizes the changes in the Company’s valuation allowance:

	Balance at January 1, 2012	$	21,579
	Increases in current period tax positions		—
	Decreases in current period tax positions		(2,059	)
	Balance at December 31, 2012	$	19,520
	Increases in current period tax positions		—
	Decreases in current period tax positions		(5,965	)
	Balance at December 31, 2013	$	13,555
	Increases in current period tax positions		—
	Decreases in current period tax positions		(3,176	)
	Balance at December 31, 2014	$	10,379

Employee_Benefits_Tables

Employee Benefits (Tables)	12 Months Ended
Employee Benefits (Tables)	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Schedule of Significant Unobservable Inputs	The following table presents a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3):

		Level 3
	Balance, January 1, 2014	$	43,825
	Actual return on assets		7,053
	Purchases, issuances and settlements, net		76,473
	Balance, December 31, 2014	$	127,351

	The following table presents a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3):
		Level 3
	Balance, January 1, 2013	$	173,625
	Actual return on assets		10,384
	Purchases, issuances and settlements, net		(140,184	)
	Balance, December 31, 2013	$	43,825

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
		2014				2013				2014			2013
	Change in benefit obligation
	Benefit obligation at January 1	$	1,494,132			$	1,621,244			$	561,923		$	687,082
	Service cost		31,773				37,872				11,058			15,282
	Interest cost		76,652				68,096				28,605			28,700
	Plan participants' contributions		—				—				2,625			2,514
	Actuarial (gain) loss		255,762				(180,688	)			123,342			(148,410	)
	Gross benefits paid		(111,863	)			(52,392	)			(26,440	)		(25,263	)
	Federal subsidy		—				—				2,159			2,018
	Benefit obligation at December 31	$	1,746,456			$	1,494,132			$	703,272		$	561,923

	Change in Plan Assets
	Fair value of plan assets at January 1	$	1,383,621			$	1,157,697			$	474,718		$	433,260
	Actual return on plan assets		116,363				208,821				48,989			36,202
	Employer contributions		40,039				69,495				12,156			28,005
	Plan participants' contributions		—				—				2,625			2,514
	Benefits paid		(111,863	)			(52,392	)			(26,440	)		(25,263	)
	Fair value of plan assets at December 31	$	1,428,160			$	1,383,621			$	512,048		$	474,718

	Funded status at December 31	$	(318,296	)		$	(110,511	)		$	(191,224	)	$	(87,205	)

	Amounts recognized in the balance sheet consist of:
	Noncurrent asset	$	—			$	—			$	1,326		$	1,271
	Current liability		(1,928	)			(1,969	)			(48	)		(57	)
	Noncurrent liability		(316,368	)			(108,542	)			(192,502	)		(88,419	)
	Net amount recognized	$	(318,296	)		$	(110,511	)		$	(191,224	)	$	(87,205	)

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
		2014				2013				2014			2013

	Net actuarial loss	$	379,743			$	145,376			$	119,566		$	17,632
	Prior service cost (credit)		3,694				4,418				(12,330	)		(14,519	)
	Net amount recognized	$	383,437			$	149,794			$	107,236		$	3,113
	Regulatory assets	$	248,641			$	90,380			$	107,236		$	3,113
	Accumulated other comprehensive income		134,796				59,414				—			—
		$	383,437			$	149,794			$	107,236		$	3,113

Schedule of Accumulated and Projected Benefit Obligations	At December 31, 2014 and 2013, 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
			2014				2013
	Projected benefit obligation		$	1,746,000			$	1,494,000
	Fair value of plan assets			1,428,000				1,384,000

			Accumulated Benefit
			Obligation Exceeds the
			Fair Value of Plans' Assets
			2014				2013
	Accumulated benefit obligation		$	1,616,000			$	43,000
	Fair value of plan assets			1,428,000				17,000

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
	2015 expected employer contributions
	To plan trusts			$	28,000			$	26,500
	To plan participants				1,929				104

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
	2015		$	63,355			$	27,897			$	2,113
	2016			69,673				30,672				2,295
	2017			75,894				33,518				2,486
	2018			82,063				36,502				2,678
	2019			88,635				39,172				2,892
	2020—2024			528,913				226,602				18,220

Schedule of Significant Assumptions of Pension and Postretirement Benefit Plans	The significant assumptions related to the Company’s pension and other postretirement benefit plans are as follows:

			Pension Benefits												Other Benefits
			2014				2013				2012				2014				2013				2012
	Weighted-average
	assumptions used to
	determine December 31
	benefit obligations
	Discount rate			4.24%				5.12%				4.17%				4.24	%			5.1	%			4.16	%
	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 2014				7.00% in 2013				7.25% in 2012
															to 5.00% in 2021+				to 5.00% in 2019+				to 5.00% in 2019+

	Weighted-average
	assumptions used to
	determine net periodic cost
	Discount rate			5.12%				4.17%				5.02%				5.1	%			4.16	%			5.05	%
	Expected return on plan assets			6.91%				7.49%				7.75%				5.87	%			6.99	%			7.41	%
	Rate of compensation increase			3.15%				3.19%				3.25%			N/A				N/A				N/A
	Medical trend		N/A				N/A				N/A				graded from				graded from				graded from
															7.00% in 2014				7.25% in 2013				7.50% in 2012
															to 5.00% in 2019+				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		$	5,943			$	(4,887	)
	Effect on other postretirement benefit obligation		$	105,967			$	(86,179	)

Components of Net Periodic Benefit Costs	The following table provides the components of net periodic benefit costs for the years ended December 31:

		2014				2013				2012
	Components of net periodic pension benefit cost
	Service cost	$	31,773			$	37,872			$	34,209
	Interest cost		76,652				68,096				70,866
	Expected return on plan assets		(94,838	)			(88,429	)			(79,272	)
	Amortization of:
	Prior service cost (credit)		724				724				723
	Actuarial (gain) loss		(131	)			37,170				29,636
	Settlement loss		—				—				7,135
	Net periodic pension benefit cost	$	14,180			$	55,433			$	63,297

	Other changes in plan assets and benefit obligations recognized in other
	comprehensive income
	Amortization of prior service credit (cost)	$	(166	)		$	(174	)		$	(176	)
	Current year actuarial (gain) loss		46,119				(73,472	)			26,425
	Amortization of actuarial gain (loss)		31				(8,911	)			(7,301	)
	Total recognized in other comprehensive income	$	45,984			$	(82,557	)		$	18,948
	Total recognized in net periodic benefit cost and comprehensive income	$	60,164			$	(27,124	)		$	82,245

	Components of net periodic other postretirement benefit cost
	Service cost	$	11,058			$	15,282			$	14,207
	Interest cost		28,605				28,700				31,570
	Expected return on plan assets		(27,500	)			(30,285	)			(28,711	)
	Amortization of:
	Prior service cost (credit)		(81	)			(2,189	)			(1,915	)
	Actuarial (gain) loss		(2,189	)			11,128				9,537
	Other		—				—				(696	)
	Net periodic other postretirement benefit cost	$	9,893			$	22,636			$	23,992

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 2015 are as follows:

		Pension Benefits				Other Benefits
	Actuarial (gain) loss	$	25,108			$	5,009
	Prior service cost (credit)		754				(2,189	)
	Total	$	25,862			$	2,820

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 at December 31, 2014, by asset category, follow:

	Asset Category		Target				Total				Quoted Prices			Significant				Significant				Percentage of Plan
			Allocation								in Active			Observable				Unobservable				Assets at
			2015								Markets for			Inputs				Inputs				December 31, 2014
											Identical Assets			(Level 2)				(Level 3)
											(Level 1)
	Cash			—			$	8,370			$	8,370		$	—			$	—				—
	Equity securities:
	U.S. large cap			24	%			342,081				342,081			—				—				24	%
	U.S. small cap value			8	%			116,503				116,503			—				—				8	%
	International			20	%			274,143				—			274,143				—				19	%
	Fixed income securities:			40	%																		41	%
	U.S. Treasury and government bonds			—				140,057				121,351			18,706				—				—
	Corporate bonds			—				376,939				—			376,939				—				—
	Mortgage-backed securities			—				4,285				—			4,285				—				—
	Long duration bond fund			—				6,555				6,555			—				—				—
	Guaranteed annuity contracts			—				51,517				—			8,987				42,530				—
	Real estate			6	%			84,821				—			—				84,821				6	%
	REITs			2	%			22,889				—			22,889				—				2	%
	Total			100	%		$	1,428,160			$	594,860		$	705,949			$	127,351				100	%

	The fair values and asset allocations of pension plan assets at December 31, 2013, by asset category, follow:

	Asset Category		Target				Total				Quoted Prices			Significant				Significant				Percentage of Plan
			Allocation								in Active			Observable				Unobservable				Assets at
			2014								Markets for			Inputs				Inputs				December 31, 2013
											Identical Assets			(Level 2)				(Level 3)
											(Level 1)
	Cash			—			$	12,844			$	12,844		$	—			$	—				—
	Equity securities:
	U.S. large cap			24	%			455,068				455,068			—				—				33	%
	U.S. small cap value			8	%			139,571				139,571			—				—				10	%
	International			20	%			295,226				615			294,611				—				21	%
	Fixed income securities:			40	%																		35	%
	U.S. Treasury and government bonds			—				81,200				76,222			4,978				—				—
	Corporate bonds			—				209,500				—			209,500				—				—
	Mortgage-backed securities			—				116,956				—			116,956				—				—
	Long duration bond fund			—				5,177				5,177			—				—				—
	Guaranteed annuity contracts			—				52,772				—			8,947				43,825				—
	Real estate			6	%			—				—			—				—				—
	REITs			2	%			15,307				—			15,307				—				1	%
	Total			100	%		$	1,383,621			$	689,497		$	650,299			$	43,825				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 at December 31, 2014, by asset category, follow:

	Asset Category		Target				Total				Quoted Prices			Significant				Significant				Percentage of Plan
			Allocation								in Active			Observable				Unobservable				Assets at
			2015								Markets for			Inputs				Inputs				December 31, 2014
											Identical Assets			(Level 2)				(Level 3)
											(Level 1)
	Bargain VEBA:
	Cash			—			$	189			$	189		$	—				—				—
	Equity securities:
	U.S. large cap			9	%			34,168				34,168			—				—				9	%
	U.S. small cap value			—				—				—			—				—				—
	International			11	%			40,232				40,232			—				—				10	%
	Fixed income securities:			80	%																		81	%
	U.S. Treasury securities and government bonds			—				155,087				155,087			—				—				—
	Corporate bonds			—				168,317				—			168,317				—				—
	Long duration bond fund			—				3,245				3,245			—				—				—
	Future and option contracts (a)			—				387				387			—				—				—
	Total bargain VEBA			100	%		$	401,625			$	233,308		$	168,317				—				100	%
	Non-bargain VEBA:
	Cash			—			$	636			$	636		$	—				—				—
	Equity securities:
	U.S. large cap			21	%			21,966				21,966			—				—				21	%
	U.S. small cap value			21	%			21,123				21,122			1				—				21	%
	International			28	%			28,611				28,611			—				—				28	%
	Fixed income securities:			30	%																		30	%
	Core fixed income bond fund			—				30,762				30,762			—				—				—
	Total non-bargain VEBA			100	%		$	103,098			$	103,097		$	1				—				100	%
	Life VEBA:
	Cash			—			$	65			$	65		$	—				—				—
	Equity securities:
	U.S. large cap			70	%			4,924				4,924			—				—				67	%
	Fixed income securities:			30	%																		33	%
	Core fixed income bond fund			—				2,336				2,336			—				—				—
	Total life VEBA			100	%		$	7,325			$	7,325		$	—				—				100	%
	Total			100	%		$	512,048			$	343,730		$	168,318				—				100	%

	(a)	Includes cash for margin requirements.
	The fair values and asset allocations of postretirement benefit plan assets at December 31, 2013, by asset category, follow:

	Asset Category		Target				Total				Quoted Prices			Significant				Significant				Percentage of Plan
			Allocation								in Active			Observable				Unobservable				Assets at
			2014								Markets for			Inputs				Inputs				December 31, 2013
											Identical Assets			(Level 2)				(Level 3)
											(Level 1)
	Bargain Veba:
	Cash			—			$	689			$	689		$	—				—				—
	Equity securities:
	U.S. large cap			18	%			72,108				72,108			—				—				19	%
	U.S. small cap value			7	%			26,574				26,574			—				—				7	%
	International			15	%			55,888				55,888			—				—				15	%
	Fixed income securities:			60	%																		59	%
	U.S. Treasury securities and government bonds			—				95,010				91,578			3,432				—				—
	Corporate bonds			—				117,843				—			117,843				—				—
	Long duration bond fund			—				2,043				2,043			—				—				—
	Future and option contracts (a)			—				620				620			—				—				—
	Total bargain VEBA			100	%		$	370,775			$	249,500		$	121,275				—				100	%
	Non-bargain VEBA:
	Cash			—			$	3,451			$	3,451		$	—				—				—
	Equity securities:
	U.S. large cap			21	%			41,430				41,430			—				—				43	%
	U.S. small cap value			21	%			—				—			—				—				0	%
	International			28	%			27,739				27,739			—				—				29	%
	Fixed income securities:			30	%																		28	%
Core fixed income bond fund			—				23,563				23,563			—				—				—
Total non-bargain VEBA			100	%		$	96,183			$	96,183		$	—				—				100	%
Life VEBA:
Cash			—			$	27			$	27		$	—				—				—
Equity securities:
U.S. large cap			70	%			5,527				5,527			—				—				71	%
Fixed income securities:			30	%																		29	%
Core fixed income bond fund			—				2,206				2,206			—				—				—
Total Life VEBA			100	%		$	7,760			$	7,760		$	—				—				100	%
Total			100	%		$	474,718			$	353,443		$	121,275				—				100	%

(a)	Includes cash for margin requirements.

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	12 Months Ended
Earnings Per Common Share (Tables)	Dec. 31, 2014
Earnings Per Share [Abstract]
Reconciliation Income (Loss) from Continuing Operations, (Loss) from Discontinued Operations and Net Income (Loss) and Weighted Average Common Shares Outstanding for Calculating Basic Net Earnings (Loss) Per Share	The following is a reconciliation of the Company’s income from continuing operations, loss from discontinued operations and net income and weighted-average common shares outstanding for calculating basic earnings per share:

		Years Ended December 31,
	Basic	2014			2013			2012
	Income from continuing operations	$	429,841		$	370,844		$	373,602
	Loss from discontinued operations, net of tax		(6,733	)		(1,580	)		(15,532	)
	Net income		423,108			369,264			358,070
	Less: Distributed earnings to common shareholders		217,253			150,038			214,541
	Less: Distributed earnings to participating securities		63			60			86
	Undistributed earnings		205,792			219,166			143,443
	Undistributed earnings allocated to common shareholders		205,735			219,082			143,385
	Undistributed earnings allocated to participating securities		57			84			58
	Total income from continuing operations available to	$	429,721		$	370,700		$	373,458
	common shareholders, basic	$	429,721		$	370,700		$	373,458
	Total income available to common shareholders, basic	$	422,988		$	369,120		$	357,926

	Weighted-average common shares outstanding, basic		178,888			177,814			176,445
	Basic earnings per share: (a)
	Income from continuing operations	$	2.4		$	2.08		$	2.12
	Loss from discontinued operations, net of tax	$	(0.04	)	$	(0.01	)	$	(0.09	)
	Net income	$	2.36		$	2.08		$	2.03
	(a)Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.
Reconciliation of Income (Loss) from Continuing Operations, (Loss) from Discontinued Operations and Net Income (Loss) and Weighted Average Common Shares Outstanding for Calculating Diluted Earnings (Loss) Per Share	The following is a reconciliation of the Company’s income from continuing operations, loss from discontinued operations and net income and weighted-average common shares outstanding for calculating diluted earnings per share:

		Years Ended December 31,
	Diluted	2014			2013			2012
	Total income from continuing operations available to	$	429,721		$	370,700		$	373,458
	common shareholders, basic	$	429,721		$	370,700		$	373,458
	Loss from discontinued operations, net of tax		(6,733	)		(1,580	)		(15,532	)
	Total income available to common shareholders, basic		422,988			369,120			357,926
	Undistributed earnings for participating securities		57			84			58
	Total income from continuing operations available to	$	429,778		$	370,784		$	373,516
	common shareholders, diluted	$	429,778		$	370,784		$	373,516
	Total income available to common shareholders, diluted	$	423,045		$	369,204		$	357,984

	Weighted-average common shares outstanding, basic		178,888			177,814			176,445
	Common stock equivalents:
	Restricted stock units		454			510			618
	Stock options		463			730			607
	Employee stock purchase plan		1			2			1
	Weighted-average common shares outstanding, diluted		179,806			179,056			177,671
	Diluted earnings per share (a)
	Income from continuing operations	$	2.39		$	2.07		$	2.1
	Loss from discontinued operations, net of tax	$	(0.04	)	$	(0.01	)	$	(0.09	)
	Net income	$	2.35		$	2.06		$	2.01
	(a)Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.
Potentially Dilutive Common Stock Equivalents Were Not Included in Earnings (Loss) Per Share Calculations Because They Were Anti-Dilutive	The following potentially dilutive common stock equivalents were not included in the earnings per share calculations for the years ended December 31 because they were anti-dilutive:

		2014			2013			2012
	Stock options		323			327			619
	Restricted stock units where certain performance		—			20			19
	conditions were not met		—			20			19

Fair_Values_of_Financial_Instr1

Fair Values of Financial Instruments (Tables)	12 Months Ended
Fair Values of Financial Instruments (Tables)	Dec. 31, 2014
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 are as follows:

		Carrying				At Fair Value as of December 31, 2014
		Amount				Level 1				Level 2			Level 3		Total
	Preferred stock with mandatory redemption	$	17,151			$ —				$ —			$	22,167	$	22,167
	requirements	$	17,151			$ —				$ —			$	22,167	$	22,167
	Long-term debt (excluding capital lease		5,491,341				2,874,622				1,474,708			2,055,058		6,404,388
	obligations)		5,491,341				2,874,622				1,474,708			2,055,058		6,404,388

		Carrying				At Fair Value as of December 31, 2013
		Amount				Level 1				Level 2			Level 3		Total
	Preferred stock with mandatory redemption	$	18,827			$ —				$ —			$	22,795	$	22,795
	requirements	$	18,827			$ —				$ —			$	22,795	$	22,795
	Long-term debt (excluding capital lease		5,224,492				2,263,355				1,462,404			2,057,506		5,783,265
	obligations)		5,224,492				2,263,355				1,462,404			2,057,506		5,783,265

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, 2014 and 2013, respectively:

	Recurring Fair Value Measures			At Fair Value as of December 31, 2014
				Level 1				Level 2				Level 3	Total
	Assets:
	Restricted funds			$	45,182			$ —				$ —	$	45,182
	Rabbi trust investments			—					11,751			—		11,751
	Deposits				4,158			—				—		4,158
	Mark-to-market derivative asset			—					3,636			—		3,636
	Total assets				49,340				15,387			—		64,727

	Liabilities:
	Deferred compensation obligation			—					11,765			—		11,765
	Mark-to-market derivative liability			—					1,012			—		1,012
	Total liabilities			—					12,777			—		12,777
	Total net assets			$	49,340			$	2,610			$ —	$	51,950

	Recurring Fair Value Measures			At Fair Value as of December 31, 2013
				Level 1				Level 2				Level 3	Total
	Assets:
	Restricted funds			$	29,259			$ —				$ —	$	29,259
	Rabbi trust investments			—					444			—		444
	Deposits				1,901			—				—		1,901
	Mark-to-market derivative asset			—					4,776			—		4,776
	Total assets				31,160				5,220			—		36,380

	Liabilities:
	Deferred compensation obligation			—					11,928			—		11,928
	Mark-to-market derivative liability			—					1,276			—		1,276
	Total liabilities			—					13,204			—		13,204
	Total net assets (liabilities)			$	31,160			$	(7,984	)		$ —	$	23,176

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Summarized Segment Information	The following table includes the Company’s summarized segment information:

		As of or for the Year Ended
		31-Dec-14
		Regulated Businesses		Market-Based Operations		Other			Consolidated
	Net operating revenues	$	2,674,329	$	354,679	$	(17,680	)	$	3,011,328
	Depreciation and amortization		394,097		5,790		24,197			424,084
	Total operating expenses, net		1,725,651		299,549		(16,448	)		2,008,752
	Income from continuing operations before		707,449		57,539		(55,174	)		709,814
	income taxes
	Total assets		14,342,837		314,253		1,473,866			16,130,956
	Capital expenditures		946,306		9,813	—				956,119
	Capital expenditures of discontinued operations	—			12	—				12
	(included in capital expenditures above)

		As of or for the Year Ended
		31-Dec-13
		Regulated Businesses		Market-Based Operations		Other			Consolidated
	Net operating revenues (1)	$	2,593,918	$	302,541	$	(17,523	)	$	2,878,936
	Depreciation and amortization (1)		375,939		6,012		24,766			406,717
	Total operating expenses, net (1)		1,700,052		252,302		(21,734	)		1,930,620
	Income from continuing operations before		654,834		53,104		(100,001	)		607,937
	income taxes (1)
	Total assets		13,447,696		286,048		1,354,398			15,088,142
	Assets of discontinued operations (included	—			7,761	—				7,761
	in total assets above)
	Capital expenditures		973,301		6,951	—				980,252
	Capital expenditures of discontinued operations	—			517	—				517
	(included in capital expenditures above)

		As of or for the Year Ended
		31-Dec-12
		Regulated Businesses		Market-Based Operations		Other			Consolidated
	Net operating revenues (1)	$	2,564,434	$	307,366	$	(17,874	)	$	2,853,926
	Depreciation and amortization (1)		349,629		5,560		25,213			380,402
	Total operating expenses, net (1)		1,685,734		266,005		(21,917	)		1,929,822
	Income from continuing operations before		649,117		44,948		(63,676	)		630,389
	income taxes (1)
	Total assets		12,680,856		260,255		1,777,865			14,718,976
	Assets of discontinued operations (included	—			7,646	—				7,646
	in total assets above)
	Capital expenditures		921,500		7,074	—				928,574
	Capital expenditures of discontinued operations		2,884		705	—				3,589
	(included in capital expenditures above)

Unaudited_Quarterly_Data_Table

Unaudited Quarterly Data (Tables)	12 Months Ended
Unaudited Quarterly Data (Tables)	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Schedule Of Unaudited Quarterly Data	The following table sets forth certain supplemental unaudited consolidated quarterly financial data for each of the four quarters in the years ended December 31, 2014 and 2013, respectively. The operating results for any quarter are not indicative of results that may be expected for a full year or any future periods:

	2014	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
		(In thousands, except per share data)
	Net operating revenues	$	679,003	$	754,778	$	846,169	$	731,378
	Operating income		187,442		254,788		337,285		223,061
	Income from continuing operations		69,113		110,174		156,608		93,946
	Net income		68,123		109,299		152,185		93,501
	Basic earnings per common share:
	Income from continuing operations		0.39		0.62		0.87		0.52
	Net income		0.38		0.61		0.85		0.52
	Diluted earnings per common share:
	Income from continuing operations		0.39		0.61		0.87		0.52
	Net income		0.38		0.61		0.85		0.52

	2013	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
		(In thousands, except per share data)
	Net operating revenues	$	631,939	$	718,565	$	822,190	$	706,242
	Operating income		165,324		242,031		323,166		217,795
	Income from continuing operations		58,445		101,369		149,909		61,121
	Net income		57,643		101,263		150,665		59,693
	Basic earnings per common share:
	Income from continuing operations		0.33		0.57		0.84		0.34
	Net income		0.32		0.57		0.85		0.33
	Diluted earnings per common share:
	Income from continuing operations		0.33		0.57		0.84		0.34
	Net income		0.32		0.57		0.84		0.33

Significant_Accounting_Policie2

Significant Accounting Policies - Additional Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Joint Venture Investments [Line Items]
Voting interest	50.00%
Estimated refunds	$18,366	$17,308
Amortization of contributions in aid of construction	23,913	22,363	20,979
Remediation costs accrued	2,200	3,300
Accrual for environmental loss contingencies payments	1,100
Regulatory assets	7,791	8,027
Deferred income taxes	86,601	17,722
Market-Based Operations
Joint Venture Investments [Line Items]
Number of business reporting units for market based services	3
Minimum
Joint Venture Investments [Line Items]
Nonutility property estimated useful life	3 years
Minimum \| Operations And Maintenance
Joint Venture Investments [Line Items]
Agreements range	2 years
Maximum
Joint Venture Investments [Line Items]
Nonutility property estimated useful life	50 years
Maximum \| Military Services Agreements \| Water Plant
Joint Venture Investments [Line Items]
Agreements range	50 years
Maximum \| Operations And Maintenance
Joint Venture Investments [Line Items]
Agreements range	40 years
Software
Joint Venture Investments [Line Items]
Acquisition cost, carrying value	$319,517	$303,798

Acquisitions_and_Divestitures_1

Acquisitions and Divestitures - Additional Information (Details) (USD $)	1 Months Ended			0 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	31-May-12	Nov. 30, 2014	Jan. 31, 2012	Nov. 14, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	1-May-12
	31-May-12	Nov. 30, 2014	Jan. 31, 2012	Customers	Dec. 31, 2012	Investment	Investment	1-May-12
Business Acquisition And Divestitures [Line Items]
Purchase price allocation, assets acquired, plant							$67,403
Purchase price allocation, liabilities assumed							43,745
Contributions in aid of construction						1,074,872	1,042,704
Debt related to purchase price allocation						1,683	12,673
Purchase price allocation, contributions in aid of construction							25,654
Goodwill					1,207,250	1,208,043	1,207,764
Ohio \| Subsidiary
Business Acquisition And Divestitures [Line Items]
Proceeds from sale of stock	102,154
Gain (loss) on sale of assets included in discontinued operation	-4,095
Terratec Environmental Limited
Business Acquisition And Divestitures [Line Items]
Proceeds from sale of stock		1,455
Gain (loss) on sale of assets included in discontinued operation		-1,454
Arizona And New Mexico Subsidiaries
Business Acquisition And Divestitures [Line Items]
Proceeds from sale of stock			458,860
Gain (loss) on sale of assets included in discontinued operation			-2,198
Dale Service Corporation
Business Acquisition And Divestitures [Line Items]
Purchase price				5,090
Purchase price allocation, assets acquired, plant				40,999
Purchase price allocation, liabilities assumed				35,909
Debt related to purchase price allocation				12,570
Purchase price allocation, contributions in aid of construction				19,163
Purchase price allocation, cash acquired				6,910
Business acquisition, number of customers acquired				20,000
Aqua New York, Inc.
Business Acquisition And Divestitures [Line Items]
Purchase price					36,688
Purchase price allocation, assets acquired, plant								59,139
Purchase price allocation, liabilities assumed								66,039
Debt related to purchase price allocation								25,215
Purchase price allocation, contributions in aid of construction								1,060
Purchase price allocation, assets acquired								102,727
Purchase price allocation, regulatory assets								27,400
Goodwill								12,181
Purchase price allocation, regulatory liabilities								11,885
Purchase price allocation, deferred taxes								15,424
Purchase price allocation, other liabilities								1,708
Purchase price allocation, pension and postretirement welfare liabilities								9,710
Other Nine Acquisitions
Business Acquisition And Divestitures [Line Items]
Purchase price allocation, liabilities assumed					4,642
Purchase price allocation, assets acquired					12,514
Regulated Water and Wastewater Systems
Business Acquisition And Divestitures [Line Items]
Business acquisition, number of companies acquired					10	13	15
Purchase price					44,560	8,935	23,658
Purchase price allocation, assets acquired, plant						16,592
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest						354
Purchase price allocation, liabilities assumed						7,745
Contributions in aid of construction						4,741
Debt related to purchase price allocation						$1,683

Summary_of_Discontinued_Operat

Summary of Discontinued Operations Presented in Consolidated Statements of Operations and Comprehensive Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquisitions And Discontinued Operations [Line Items]
Income (loss) from discontinued operations	($6,733)	($1,580)	($15,532)
Terratec Environmental Limited
Acquisitions And Discontinued Operations [Line Items]
Operating revenues	13,614	22,922	42,341
Total operating expenses, net	19,482	25,389	49,726
Operating loss	-5,868	-2,467	-7,385
Other income (expenses), net			-167
Income (loss) from discontinued operations before income taxes	-5,868	-2,467	-7,552
Provision (benefit) for income taxes	865	-887	7,980
Income (loss) from discontinued operations	($6,733)	($1,580)	($15,532)

Summary_of_Reclassified_Assets

Summary of Reclassified Assets Discontinued Operations Held For Sale and Liabilities Discontinued Operations Held For Sale (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
ASSETS
Current assets	$7,761
Total assets of discontinued operations	7,761	7,646
LIABILITIES
Current liabilities	3,824
Terratec Environmental Limited
ASSETS
Total property, plant and equipment			2,808
Current assets			4,953
Total assets of discontinued operations			7,761
LIABILITIES
Current liabilities			3,824
Total liabilities of discontinued operations			$3,824

Schedule_of_Major_Classes_of_U

Schedule of Major Classes of Utility Plant by Category (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Public Utility Property Plant And Equipment [Line Items]
Construction work in progress	$303,004	$275,202
Utility plant, gross	16,891,384	16,138,685
Less accumulated depreciation	3,991,680	3,894,326
Utility plant, net	12,899,704	12,244,359
Water Plant \| Land and Other Non-Depreciable Assets
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	137,199	132,295
Water Plant \| Sources of Supply
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	680,623	659,249
Water Plant \| Sources of Supply \| Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	11 years
Water Plant \| Sources of Supply \| Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	127 years
Water Plant \| Treatment and Pumping Facilities
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	2,969,411	3,006,140
Water Plant \| Treatment and Pumping Facilities \| Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	3 years
Water Plant \| Treatment and Pumping Facilities \| Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	101 years
Water Plant \| Transmission and Distribution Facilities
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	7,962,759	7,489,208
Water Plant \| Transmission and Distribution Facilities \| Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	9 years
Water Plant \| Transmission and Distribution Facilities \| Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	156 years
Water Plant \| Services, Meters and Fire Hydrants
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	3,062,568	2,898,293
Water Plant \| Services, Meters and Fire Hydrants \| Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	9 years
Water Plant \| Services, Meters and Fire Hydrants \| Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	122 years
Water Plant \| General Structures and Equipment
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	1,035,857	995,186
Water Plant \| General Structures and Equipment \| Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	1 year
Water Plant \| General Structures and Equipment \| Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	154 years
Wastewater Plant
Public Utility Property Plant And Equipment [Line Items]
Utility plant excluding Construction work in progress	$739,963	$683,112
Wastewater Plant \| Minimum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	2 years
Wastewater Plant \| Maximum
Public Utility Property Plant And Equipment [Line Items]
Range of Remaining Useful Lives	115 years

Utility_Plant_Additional_Infor

Utility Plant - Additional Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure Utility Plant Additional Information [Abstract]
Depreciation expense	$356,952	$337,653	$314,639
Provision for depreciation, percentage of aggregate average depreciable asset	2.94%	2.94%	2.94%

Schedule_of_Allowances_for_Unc

Schedule of Allowances for Uncollectible Accounts (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure Schedule Of Allowances For Uncollectible Accounts [Abstract]
Balance at January 1	($33,823)	($26,744)	($18,902)
Amounts charged to expense	-36,717	-26,953	-26,701
Amounts written off	42,886	23,914	22,607
Recoveries of amounts written off	-7,287	-4,040	-3,748
Balance at December 31	($34,941)	($33,823)	($26,744)

Components_of_Regulatory_Asset

Components of Regulatory Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Regulatory Asset [Line Items]
Regulatory assets	$1,153,429	$858,465
Income Taxes Recoverable through Rates
Regulatory Asset [Line Items]
Regulatory assets	228,601	242,902
Debt and Preferred Stock Expense
Regulatory Asset [Line Items]
Regulatory assets	71,403	72,349
Deferred Pension Expense
Regulatory Asset [Line Items]
Regulatory assets	263,486	109,799
Deferred Other Postretirement Benefit Expense
Regulatory Asset [Line Items]
Regulatory assets	106,792	3,653
Deferred Business Services Project Expense
Regulatory Asset [Line Items]
Regulatory assets	7,530	7,763
Deferred Tank Painting Costs
Regulatory Asset [Line Items]
Regulatory assets	37,207	33,519
Deferred Rate Case Expense
Regulatory Asset [Line Items]
Regulatory assets	6,785	9,407
Purchase Premium Recoverable through Rates
Regulatory Asset [Line Items]
Regulatory assets	60,412	60,787
Environmental Remediation Recoverable through Rates
Regulatory Asset [Line Items]
Regulatory assets	7,791	8,027
Coastal Water Project Costs
Regulatory Asset [Line Items]
Regulatory assets	8,386	16,826
San Clemente Dam Project Costs
Regulatory Asset [Line Items]
Regulatory assets	71,891	44,404
Removal Costs Recoverable through Rates
Regulatory Asset [Line Items]
Regulatory assets	163,123	126,771
Regulatory Balancing Accounts
Regulatory Asset [Line Items]
Regulatory assets	60,043	63,083
Other
Regulatory Asset [Line Items]
Regulatory assets	$59,979	$59,175

Regulatory_Assets_and_Liabilit2

Regulatory Assets and Liabilities - Additional Information (Details) (USD $)	0 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2008	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Removal Costs Recovered through Rates
Regulatory Asset And Liabilities [Line Items]
Amortization of regulatory assets	$48,000
Amortization of regulatory assets period end date	2048-11
Debt and Preferred Stock Expense
Regulatory Asset And Liabilities [Line Items]
Regulatory assets amortization period		30 years
Deferred Pension Expense
Regulatory Asset And Liabilities [Line Items]
Regulatory assets underfunded status		248,641	90,380
Deferred Other Postretirement Benefit Expense
Regulatory Asset And Liabilities [Line Items]
Regulatory assets underfunded status		107,236	3,113
Deferred Security Costs \| Minimum
Regulatory Asset And Liabilities [Line Items]
Regulatory assets amortization period		5 years
Deferred Security Costs \| Maximum
Regulatory Asset And Liabilities [Line Items]
Regulatory assets amortization period		10 years
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
Deferred Rate Case Expense
Regulatory Asset And Liabilities [Line Items]
Regulatory assets amortization period		3 years
Coastal Water Project Costs
Regulatory Asset And Liabilities [Line Items]
Deferred regulatory assets		1,923	1,299	1,987
San Clemente Dam Project Costs
Regulatory Asset And Liabilities [Line Items]
Pre-construction costs to be recovered via surcharge		24,303
Pre-construction costs recovery period		20 years
Surcharges collections		4,531	3,753
Other deferred costs		26,023	12,394
San Clemente Dam Project Costs \| Maximum
Regulatory Asset And Liabilities [Line Items]
Estimated additional pre-construction costs		49,000
San Clemente Dam Project Costs \| Maximum \| Dam Safety Measure
Regulatory Asset And Liabilities [Line Items]
Estimated additional pre-construction costs		2,500

Components_of_Regulatory_Liabi

Components of Regulatory Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Regulatory Liabilities [Line Items]
Regulatory liabilities	$391,782	$373,319
Removal Costs Recovered through Rates
Regulatory Liabilities [Line Items]
Regulatory liabilities	300,635	301,537
Pension and Other Postretirement Benefit Balancing Accounts
Regulatory Liabilities [Line Items]
Regulatory liabilities	53,734	40,837
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities	$37,413	$30,945

Summary_of_Changes_in_Goodwill

Summary of Changes in Goodwill Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Line Items]
Cost, beginning balance	$3,648,053	$3,647,539
Total Net, beginning balance	1,207,764	1,207,250
Goodwill from acquisitions	354	428
Reclassifications and other activity	-75	86
Cost, ending balance	3,648,332	3,648,053
Total Net, ending balance	1,208,043	1,207,764
Accumulated Impairment	-2,440,289	-2,440,289	-2,440,289
Regulated Unit
Goodwill [Line Items]
Cost, beginning balance	3,412,063	3,411,549
Goodwill from acquisitions	354	428
Reclassifications and other activity	-75	86
Cost, ending balance	3,412,342	3,412,063
Accumulated Impairment	-2,332,670	-2,332,670	-2,332,670
Market-Based Operations
Goodwill [Line Items]
Cost, beginning balance			235,990
Cost, ending balance	235,990	235,990	235,990
Accumulated Impairment	($107,619)	($107,619)	($107,619)

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Details) (USD $)	0 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 12, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2014	Dec. 31, 2011
Stockholders Equity Note [Line Items]
Declared cash dividend per share	$0.31
Dividend payable, date declared	12-Dec-14
Dividend payable, record date	9-Feb-15
Dividend payable, date to be paid	2-Mar-15
Dividends accrued		$55,552
Stock-based compensation, capitalized amount		0	0	0
Stock Options
Stockholders Equity Note [Line Items]
Vesting period		3 years	3 years	3 years
Maximum terms		7 years
Unrecognized compensation cost		1,545
Weighted-average period (in years)		1 year 8 months 12 days
Total grant date fair value of stock awards		2,728	3,512	3,219
Stock Options \| Minimum
Stockholders Equity Note [Line Items]
Vesting period		1 year
Stock Options \| Maximum
Stockholders Equity Note [Line Items]
Vesting period		3 years
Restricted Stock Units
Stockholders Equity Note [Line Items]
Vesting period		3 years	3 years	3 years
Unrecognized compensation cost		4,634
Weighted-average period (in years)		1 year 4 months 24 days
Total grant date fair value of stock awards		10,829	8,891	4,191
Number of grants		228,000			113	189
Restricted shares granted		The terms of the grants specified that if certain performance on internal measures and market thresholds was achieved, the restricted stock units would vest; if performance was surpassed, up to 175% of the target awards would be distributed; and if performance thresholds were not met
Expected term		3 years
Accrued dividend equivalents		$962	$648	$1,168
Restricted Stock Units \| Minimum
Stockholders Equity Note [Line Items]
Vesting period		1 year
Restricted Stock Units \| Maximum
Stockholders Equity Note [Line Items]
Vesting period		3 years
2007 Omnibus Equity Compensation Plan
Stockholders Equity Note [Line Items]
Total shares authorized for grant		15,500,000
Shares available for grant		8,869,000
Employee Stock Purchase Plan
Stockholders Equity Note [Line Items]
Shares available for grant		1,261,000
Lesser of fair market value		90.00%
Shares issued		102,000	111,000	118,000
DRIP
Stockholders Equity Note [Line Items]
Shares available for grant		4,611,000

Summary_Information_Regarding_

Summary Information Regarding Issuances Under DRIP (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Shares of common stock issued	44	53
Cash proceeds received	$2,119	$2,171

Cash_Dividend_Payment_During_P

Cash Dividend Payment During Period (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013
Dividends [Abstract]
Dividends per share	$0.31	$0.31	$0.31	$0.28	$0.28	$0.28	$0.28
Total dividends paid	$55,506	$55,458	$55,422	$49,968	$49,896	$49,810	$49,744

Changes_in_Accumulated_Other_C

Changes in Accumulated Other Comprehensive Loss by Component, Net of Tax (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	($34,635)	($116,191)
Other comprehensive income (loss) before reclassifications	-47,397	72,471
Amounts reclassified from accumulated other comprehensive income (loss)	164	9,085
Other comprehensive income (loss)	-47,233	81,556	-18,514
Accumulated other comprehensive income (loss) Ending balance	-81,868	-34,635	-116,191
Employee Benefit Plan Funded Status
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	-69,711	-143,183
Other comprehensive income (loss) before reclassifications	-46,119	73,472
Other comprehensive income (loss)	-46,119	73,472
Accumulated other comprehensive income (loss) Ending balance	-115,830	-69,711
Amortization of Prior Service Cost
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	713	539
Amounts reclassified from accumulated other comprehensive income (loss)	166	174
Other comprehensive income (loss)	166	174
Accumulated other comprehensive income (loss) Ending balance	879	713
Amortization of Actuarial (Gain) Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	31,150	22,239
Amounts reclassified from accumulated other comprehensive income (loss)	-31	8,911
Other comprehensive income (loss)	-31	8,911
Accumulated other comprehensive income (loss) Ending balance	31,119	31,150
Foreign Currency Translation
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) Beginning balance	3,213	4,214
Other comprehensive income (loss) before reclassifications	-458	-1,001
Other comprehensive income (loss)	-458	-1,001
Accumulated other comprehensive income (loss) Ending balance	2,755	3,213
Loss on Cash Flow Hedge
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications	-820
Amounts reclassified from accumulated other comprehensive income (loss)	29
Other comprehensive income (loss)	-791
Accumulated other comprehensive income (loss) Ending balance	($791)

StockBased_Compensation_Expens

Stock-Based Compensation Expense (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation in operation and maintenance expense	$13,043	$12,474	$11,470
Income tax benefit	-5,087	-4,865	-4,473
After-tax stock-based compensation expense	7,956	7,609	6,997
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation in operation and maintenance expense	2,602	3,170	3,282
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation in operation and maintenance expense	9,848	8,718	7,658
Income tax benefit	-1,625	-2,049	-799
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation in operation and maintenance expense	$593	$586	$530

WeightedAverage_Assumptions_De

Weighted-Average Assumptions (Details) (Stock Options, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield	2.55%	2.52%	2.70%
Expected volatility	17.75%	23.50%	28.35%
Risk-free interest rate	1.06%	0.70%	0.78%
Expected life (years)	3 years 7 months 6 days	4 years 3 months 18 days	4 years 4 months 24 days
Exercise price	$44.29	$39.60	$34.14
Grant date fair value per share	$4.57	$5.78	$6.11

Summary_of_Stock_Option_Activi

Summary of Stock Option Activity (Details) (Stock Options, USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding at January 1, 2014	2,055
Granted	491
Forfeited or expired	-62
Exercised	-574
Options outstanding at December 31, 2014	1,910
Exercisable at December 31, 2014	1,094
Weighted Average Exercise Price (per share), Options outstanding at January 1, 2014	$28.80
Weighted Average Exercise Price (per share), Granted	$44.29
Weighted Average Exercise Price (per share), Forfeited or expired	$39.23
Weighted Average Exercise Price (per share), Exercised	$25.40
Weighted Average Exercise Price (per share), Options outstanding at December 31, 2014	$33.47
Weighted Average Exercise Price (per share), Options outstanding at December 31, 2014	$27.68
Weighted Average Remaining Life (years), Options outstanding at December 31, 2014	3 years 10 months 24 days
Weighted Average Remaining Life (years), Exercisable at December 31, 2014	2 years 9 months 18 days
Aggregate intrinsic Value, Options outstanding at December 31, 2014	$37,881
Aggregate intrinsic Value, Exercisable at December 31, 2014	$28,022

Additional_Information_to_Stoc

Additional Information to Stock Options Exercised (Details) (Stock Options, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options
Schedule Of Stock Options [Line Items]
Intrinsic value	$12,689	$15,102	$14,515
Exercise proceeds	14,582	20,211	22,112
Income tax benefit	$3,885	$4,383	$4,017

WeightedAverage_Assumptions_Us

Weighted-Average Assumptions Used in Monte Carlo Simulation (Details) (Restricted Stock Units, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	17.78%	19.37%	22.47%
Risk-free interest rate	0.75%	0.40%	0.43%
Expected life (years)	3 years	3 years	3 years
Grant date fair value per share	$45.45	$40.13	$37.40

Summary_of_Restricted_Stock_Un

Summary of Restricted Stock Unit Activity (Details) (Restricted Stock Units, USD $)	1 Months Ended	12 Months Ended
	Jan. 31, 2014	Dec. 31, 2014	Dec. 31, 2011
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested total at January 1, 2014	539,000	539,000
Granted	113	228,000	189
Performance share adjustment		113,000
Vested		-337,000
Forfeited		-27,000
Non-vested total at December 31, 2014		516,000
Weighted-average grant date fair value (per share), non-vested total beginning balance	$36.27	$36.27
Weighted-average grant date fair value (per share), granted		$45.45
Weighted-average grant date fair value (per share), Performance share adjustment		$30.34
Weighted-average grant date fair value (per share), vested		$32.13
Weighted-average grant date fair value (per share), forfeited		$41.61
Weighted-average grant date fair value (per share), non-vested total ending balance		$41.46

Additional_Information_to_Stoc1

Additional Information to Stock Options Activity (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Income tax benefit	$5,087	$4,865	$4,473
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value	15,539	13,983	6,159
Income tax benefit	$1,625	$2,049	$799

Components_of_LongTerm_Debt_De

Components of Long-Term Debt (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$5,474,639		$5,203,524
Unamortized debt, net	31,168	[1]	35,984	[1]
Interest rate swap fair value adjustment	3,570		4,724
Total long-term debt	5,509,377		5,244,232
Private activity bonds and government funded debt \| American Water Capital Corp. ("AWCC") \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	1.79%	[2]
Interest Rate, Maximum	6.25%	[2]
Weighted Average Rate	5.33%	[2]
Maturity Date, Minimum	2021	[2]
Maturity Date, Maximum	2040	[2]
Long-term debt	231,330	[2]	330,732	[2]
Private activity bonds and government funded debt \| Other subsidiaries
Debt Instrument [Line Items]
Long-term debt	729,170
Private activity bonds and government funded debt \| Other subsidiaries \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	0.00%	[3]
Interest Rate, Maximum	6.20%	[3]
Weighted Average Rate	4.73%	[3]
Maturity Date, Minimum	2015	[3]
Maturity Date, Maximum	2041	[3]
Long-term debt	795,472	[3]	863,716	[3]
Senior notes \| American Water Capital Corp. ("AWCC") \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	3.40%	[2]
Interest Rate, Maximum	8.27%	[2]
Weighted Average Rate	5.43%	[2]
Maturity Date, Minimum	2016	[2]
Maturity Date, Maximum	2042	[2]
Long-term debt	3,753,200	[2]	3,312,761	[2]
Mortgage bonds \| Other subsidiaries \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	4.29%
Interest Rate, Maximum	9.71%
Weighted Average Rate	7.41%
Maturity Date, Minimum	2015
Maturity Date, Maximum	2039
Long-term debt	676,500		676,500
Mandatorily redeemable preferred stock \| Other subsidiaries
Debt Instrument [Line Items]
Interest Rate, Minimum	8.47%
Interest Rate, Maximum	9.75%
Weighted Average Rate	8.60%
Maturity Date, Minimum	2019
Maturity Date, Maximum	2036
Long-term debt	17,252		18,902
Capital lease obligations \| Other subsidiaries
Debt Instrument [Line Items]
Interest Rate, Minimum	12.17%
Weighted Average Rate	12.17%
Maturity Date, Maximum	2026
Long-term debt	$885		$913

[1]	Primarily fair value adjustments previously recognized in acquisition purchase accounting.
[2]	AWCC, which is a wholly-owned subsidiary of the Company, has a strong support agreement with its parent that, under certain circumstances, is the functional equivalent of a guarantee.
[3]	Includes $10,190 and $11,920 of variable rate debt with variable-to-fixed interest rate swaps ranging between 3.93% and 4.72%, at December 31, 2014 and 2013, respectively. This debt was assumed via an acquisition in 2013.

Components_of_LongTerm_Debt_Pa

Components of Long-Term Debt (Parenthetical) (Details) (Interest Rate Swap, USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Variable rate debt	$10,190	$11,920
Minimum
Debt Instrument [Line Items]
Variable-to-fixed rate	3.93%
Maximum
Debt Instrument [Line Items]
Variable-to-fixed rate		4.72%

LongTerm_Debt_Additional_Infor

Long-Term Debt - Additional Information (Details) (USD $)	12 Months Ended
Long-Term Debt - Additional Information (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$5,474,639,000	$5,203,524,000
Line of credit facility consolidated debt to consolidated capitalization ratio	0.55			0.7
Redeemable debt, amount outstanding	1,044,990
Debt issuance cost	4,593,000
Debt assumed in an acquisition	1,683,000	12,673,000
Interest income	11,441,000	11,753,000	12,652,000
6.085% Senior Notes
Debt Instrument [Line Items]
Maturity Date, Maximum	2017
Interest Rate Swap
Debt Instrument [Line Items]
Fixed rate debt	100,000,000
Interest Rate	6.09%
Derivative description of variable rate basis	six-month LIBOR plus 3.422
Maturity Date, Maximum	2017
Interest Rate Swap \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, basis spread on variable rate	3.42%
Line of Credit
Debt Instrument [Line Items]
Line of credit facility consolidated debt to consolidated capitalization ratio	0.7
Other subsidiaries \| Mortgage bonds \| Collateralized Debt Obligations
Debt Instrument [Line Items]
Long-term debt	676,500,000
Other subsidiaries \| Private activity bonds and government funded debt
Debt Instrument [Line Items]
Long-term debt	729,170,000
Other subsidiaries \| Private activity bonds and government funded debt \| Collateralized Debt Obligations
Debt Instrument [Line Items]
Long-term debt	$795,472,000

Future_Sinking_Fund_Payments_a

Future Sinking Fund Payments and Maturities (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified	Dec. 31, 2014
Debt Disclosure [Abstract]
2015	$61,132
2016	53,353
2017	572,775
2018	455,861
2019	164,909
Thereafter	$4,166,609

LongTerm_Debt_Issued_Details

Long-Term Debt Issued (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
American Water Capital Corp. ("AWCC") \| Senior notes \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	3.40%	[1]
Interest Rate, Maximum	8.27%	[1]
American Water Capital Corp. ("AWCC") \| Private activity bonds and government funded debt \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	1.79%	[1]
Interest Rate, Maximum	6.25%	[1]
Other subsidiaries \| Private activity bonds and government funded debt \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	0.00%	[2]
Interest Rate, Maximum	6.20%	[2]
Debt issued during the year
Debt Instrument [Line Items]
Total issuances	510,474
Debt issued during the year \| American Water Capital Corp. ("AWCC") \| Senior notes \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	3.40%
Interest Rate, Maximum	4.30%
Total issuances	500,000
Debt issued during the year \| American Water Capital Corp. ("AWCC") \| Senior notes \| Minimum \| Fixed rate
Debt Instrument [Line Items]
Maturity	2025
Debt issued during the year \| American Water Capital Corp. ("AWCC") \| Senior notes \| Maximum \| Fixed rate
Debt Instrument [Line Items]
Maturity	2042
Debt issued during the year \| Other subsidiaries \| Private activity bonds and government funded debt \| Fixed rate
Debt Instrument [Line Items]
Interest Rate, Minimum	0.00%	[3]
Interest Rate, Maximum	5.00%	[3]
Total issuances	10,474	[3]
Debt issued during the year \| Other subsidiaries \| Private activity bonds and government funded debt \| Minimum \| Fixed rate
Debt Instrument [Line Items]
Maturity	2031	[3]
Debt issued during the year \| Other subsidiaries \| Private activity bonds and government funded debt \| Maximum \| Fixed rate
Debt Instrument [Line Items]
Maturity	2033	[3]

[1]	AWCC, which is a wholly-owned subsidiary of the Company, has a strong support agreement with its parent that, under certain circumstances, is the functional equivalent of a guarantee.
[2]	Includes $10,190 and $11,920 of variable rate debt with variable-to-fixed interest rate swaps ranging between 3.93% and 4.72%, at December 31, 2014 and 2013, respectively. This debt was assumed via an acquisition in 2013.
[3]	Included in the issuance amounts for other subsidiaries private activity bonds and government funded debt above was $9,977, which was initially kept in Trust pending the Companyâ€™s certification that it has incurred qualifying capital expenditures. These issuances have been presented as non-cash in the accompanying Consolidated Statements of Cash Flows. Subsequent releases of all or a lesser portion of these funds by the applicable Trust are reflected as the release of restricted funds and are included in investing activities in the accompanying Consolidated Statements of Cash Flows.

LongTerm_Debt_Issued_Parenthet

Long-Term Debt Issued (Parenthetical) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Long-term debt issued	$9,977	$6,702	$68,746

LongTerm_Debt_Retired_through_

Long-Term Debt Retired through Sinking Fund Payments and Maturities (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Other subsidiaries \| Mandatorily redeemable preferred stock
Debt Instrument [Line Items]
Interest Rate, Minimum	8.47%
Interest Rate, Maximum	9.75%
Maturity Date, Minimum	2019
Maturity Date, Maximum	2036
Debt retired during the year
Debt Instrument [Line Items]
Total retirements and redemptions	241,042
Debt retired during the year \| Other subsidiaries \| Mandatorily redeemable preferred stock
Debt Instrument [Line Items]
Interest Rate, Minimum	8.49%
Interest Rate, Maximum	9.18%
Maturity Date, Minimum	2031
Maturity Date, Maximum	2036
Total retirements and redemptions	1,650
Debt retired during the year \| Other subsidiaries \| Capital lease payments
Debt Instrument [Line Items]
Total retirements and redemptions	28
Debt retired during the year \| Fixed rate two \| American Water Capital Corp. ("AWCC") \| Private activity bonds and government funded debt
Debt Instrument [Line Items]
Interest Rate, Minimum	6.00%
Interest Rate, Maximum	6.75%
Maturity Date, Minimum	2018
Maturity Date, Maximum	2031
Total retirements and redemptions	101,085
Debt retired during the year \| Fixed rate two \| American Water Capital Corp. ("AWCC") \| Senior notes
Debt Instrument [Line Items]
Interest Rate	6.00%
Maturity Date, Maximum	2039
Total retirements and redemptions	59,561
Debt retired during the year \| Fixed rate two \| Other subsidiaries \| Private activity bonds and government funded debt
Debt Instrument [Line Items]
Interest Rate, Minimum	0.00%	[1]
Interest Rate, Maximum	5.25%	[1]
Maturity Date, Minimum	2014	[1]
Maturity Date, Maximum	2041	[1]
Total retirements and redemptions	78,718	[1]

[1]	Includes $1,021 of non-cash defeasance via the use of restricted funds.

LongTerm_Debt_Retired_through_1

Long-Term Debt Retired through Sinking Fund Payments and Maturities (Parenthetical) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
Long-term debt retired	$1,021	($3,565)

Summary_of_Derivative_Fair_Val

Summary of Derivative Fair Value Balance (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Regulatory and other long-term assets	$3,636	$4,776
Interest rate swap fair value adjustment	3,570	4,724
Interest Rate Swap
Derivative [Line Items]
Interest rate swap fair value adjustment	3,570	4,724
Other
Derivative [Line Items]
Regulatory and other long-term assets	$3,636	$4,776

Derivative_and_Hedged_Item_Det

Derivative and Hedged Item (Details) (Net Interest, Designated as Hedging Instrument, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Interest \| Designated as Hedging Instrument
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on swap	($1,140)	($3,133)	$2,085
Gain (loss) on borrowing	1,154	2,991	-1,604
Hedge ineffectiveness	$14	($142)	$481

ShortTerm_Debt_Additional_Info

Short-Term Debt - Additional Information (Details) (USD $)	12 Months Ended			1 Months Ended
Short-Term Debt - Additional Information (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013	Oct. 31, 2013	Sep. 09, 2013
Short Term Debt [Line Items]
Short-term debt	$449,959,000	$630,307,000
Commercial paper, discount	41,000	193,000
Short-term borrowings with maturities more than three months	449,959,000	630,307,000
Debt issuance costs	4,593,000	4,503,000	7,393,000
Letters of credit, outstanding amount	37,896,000	41,785,000
Line of credit facility consolidated debt to consolidated capitalization ratio	0.55				0.7
American Water Capital Corp. ("AWCC") \| Revolving Credit Facility
Short Term Debt [Line Items]
Maximum borrowing capacity				1,250,000,000		1,000,000,000
Debt issuance costs	1,126,000
American Water Capital Corp. ("AWCC") \| Credit Facility October Two Thousand Eighteen
Short Term Debt [Line Items]
Maximum borrowing capacity				1,180,000,000
New agreement expiration date				2017-10
New agreement extended expiration date				2018-10
Commercial Paper Program
Short Term Debt [Line Items]
Short-term debt	449,959,000	630,307,000
Short-term borrowings with maturities more than three months	449,959,000	630,307,000
Maximum borrowing capacity				1,000,000,000		700,000,000
Commercial Paper Program \| American Water Capital Corp. ("AWCC")
Short Term Debt [Line Items]
Maximum borrowing capacity	1,000,000,000	1,000,000,000
Maturity in More Than Three Months
Short Term Debt [Line Items]
Short-term debt	0
Short-term borrowings with maturities more than three months	$0

Schedule_of_Available_Capacity

Schedule of Available Capacity Under Commercial Paper Program (Details) (Commercial Paper Program, USD $)	Sep. 30, 2013	Sep. 09, 2013	Dec. 31, 2014	Dec. 31, 2013
Short Term Debt [Line Items]
Commercial paper program	$1,000,000,000	$700,000,000
American Water Capital Corp. ("AWCC")
Short Term Debt [Line Items]
Commercial paper program			1,000,000,000	1,000,000,000
Commercial paper program available capacity			$550,000,000	$369,500,000

Schedule_of_Line_of_Credit_Fac

Schedule of Line of Credit Facility Sub-Limits and Available Capacity (Details) (Letter of Credit, American Water Capital Corp. ("AWCC"), USD $)	Dec. 31, 2014	Dec. 31, 2013
Letter of Credit \| American Water Capital Corp. ("AWCC")
Short Term Debt [Line Items]
Letter of credit sublimit	$150,000,000	$150,000,000
Letter of credit available capacity	$112,104,000	$108,215,000

Schedule_of_ShortTerm_Borrowin

Schedule of Short-Term Borrowings Activity (Details) (American Water Capital Corp. ("AWCC"), USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
American Water Capital Corp. ("AWCC")
Short Term Debt [Line Items]
Average borrowings	$548,530	$370,420	[1]
Maximum borrowings outstanding	$745,000	$829,250	[1]
Weighted average interest rates, computed on a daily basis	0.31%	0.43%	[1]
Weighted average interest rates, ending balance	0.42%	0.36%	[1]

[1]	2013 average borrowings, maximum borrowings outstanding, and weighted average interest rates, computed on daily basis have been revised by immaterial amounts.

Components_of_General_Tax_Expe

Components of General Tax Expense from Continuing Operations (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
General Tax Expense [Line Items]
General taxes	$236,732	$234,198	$220,758
Gross receipts and franchise
General Tax Expense [Line Items]
General taxes	96,014	96,044	92,612
Property and capital stock
General Tax Expense [Line Items]
General taxes	95,651	94,394	84,448
Payroll
General Tax Expense [Line Items]
General taxes	30,698	30,985	32,335
Other general
General Tax Expense [Line Items]
General taxes	$14,369	$12,775	$11,363

Components_of_Income_Tax_Expen

Components of Income Tax Expense from Continuing Operations (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
State income taxes, current	$11,055	$7,202	$26,604
State income taxes, deferred, current	-287	-405	-280
State income taxes, deferred, non-current	30,788	26,821	24,256
State income taxes	41,556	33,618	50,580
Federal income taxes, current	14,767	-19,995	31,482
Federal income taxes, deferred, current	-1,528	-1,324	-2,031
Federal income taxes, deferred, non-current	226,572	226,295	178,274
Amortization of deferred investment tax credits	-1,394	-1,501	-1,518
Federal income taxes	238,417	203,475	206,207
Actual income tax expense	$279,973	$237,093	$256,787

Reconciliation_of_Income_Tax_E

Reconciliation of Income Tax Expense from Continuing Operations (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income tax at statutory rate	$248,424	$212,777	$220,636
State taxes, net of federal taxes	27,011	21,852	32,877
Change in valuation allowance	-2	-455	143
Flow through differences	3,467	3,217	3,032
Amortization of deferred investment tax credits	-1,394	-1,501	-1,518
Subsidiary preferred dividends	532	584	634
Sec 162(m) Adjustment	980
Other, net	955	619	983
Actual income tax expense	$279,973	$237,093	$256,787

Components_of_Net_Deferred_Tax

Components of Net Deferred Tax Liability from Continuing Operations (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Advances and contributions	$502,069	$510,122
Deferred investment tax credits	9,452	10,027
Other postretirement benefits	104,723	107,773
Tax losses and credits	197,288	265,640
Pension benefits	124,985	122,143
Unamortized debt discount, net	20,249	20,249
Other	32,159	23,001
Deferred tax assets before valuation allowance	990,925	1,058,955
Valuation allowance	-10,379	-13,555	-19,520	-21,579
Deferred tax assets, net of valuation allowance	980,546	1,045,400
Utility plant, principally due to depreciation differences	2,676,574	2,478,617
Income taxes recoverable through rates	75,538	81,135
Deferred business services project expenses	4,584	4,584
Deferred other postretirement benefits	65,157	65,071
Deferred pension benefits	121,317	169,336
Other	71,514	69,632
Deferred Tax Liabilities, Total	3,014,684	2,868,375
Deferred Tax Assets (Liabilities), Net, Total	($2,034,138)	($1,822,975)

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Examination [Line Items]
Capital loss carry forwards	$3,844	$3,844
Net of deferred tax assets and regulatory assets	6,348	6,241
Interest and penalties	157	242
Unrecognized tax benefit excluding interest and penalties, that would affect the effective tax rate	9,444	7,439
Change in valuation allowance	-2	-455	143
Federal
Income Tax Examination [Line Items]
Net operating loss carryforwards	1,004,705	1,182,075
Tax benefits on stock-based compensation	14,325
Net operating loss carryforwards expiration date	The Companyâ€™s federal NOL carryforwards do not begin expiring until 2028
State
Income Tax Examination [Line Items]
Net operating loss carryforwards	542,705	628,049
Net operating loss carryforwards expiration date	The state NOL carryforwards will expire between 2015 and 2033
Canadian
Income Tax Examination [Line Items]
Net operating loss carryforwards	6,498	6,323
Net operating loss carryforwards expiration date	The Canadian NOL carryforwards will expire between 2015 and 2033
Entity Reorganization Within Market-Based Operations Segment
Income Tax Examination [Line Items]
Change in valuation allowance		($2,979)

Changes_in_Gross_Liability_Exc

Changes in Gross Liability Excluding Interest and Penalties for Unrecognized Tax Benefits (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Beginning Balance	$177,947	$180,993
Increases in current period tax positions	53,818	27,229
Decreases in prior period measurement of tax positions	-36,528	-30,275
Ending Balance	$195,237	$177,947

Changes_in_Valuation_Allowance

Changes in Valuation Allowance (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Valuation Allowance [Line Items]
Beginning Balance				$21,579
Ending Balance	10,379	13,555	19,520	21,579
Decrease
Valuation Allowance [Line Items]
Current period tax positions	($3,176)	($5,965)	($2,059)

Employee_Benefits_Additional_I

Employee Benefits - Additional Information (Details) (USD $)	1 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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		$7,595	$7,926	$7,990
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Benefits paid		111,863	52,392
Expected employer contributions, 2015		6,100
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Benefits paid		26,440	25,263
Expected employer contributions, 2015		6,632
One-time Termination Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefits paid		$55,579

Schedule_of_Changes_in_Fair_Va

Schedule of Changes in Fair Value of Plan Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%		100.00%
Fair value of plan assets	$1,428,160		$1,383,621		$1,157,697
Percentage of Plan Assets	100.00%		100.00%
Pension Plan Asset \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	594,860		689,497
Pension Plan Asset \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	705,949		650,299
Pension Plan Asset \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	127,351		43,825
Pension Plan Asset \| Real estate
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	6.00%		6.00%
Fair value of plan assets	84,821
Percentage of Plan Assets	6.00%
Pension Plan Asset \| Real estate \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	84,821
Pension Plan Asset \| REITs
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	2.00%		2.00%
Fair value of plan assets	22,889		15,307
Percentage of Plan Assets	2.00%		1.00%
Pension Plan Asset \| REITs \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22,889		15,307
Pension Plan Asset \| Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,370		12,844
Pension Plan Asset \| Cash \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,370		12,844
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	342,081		455,068
Percentage of Plan Assets	24.00%		33.00%
Pension Plan Asset \| Equity Securities \| U.S. large cap \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	342,081		455,068
Pension Plan Asset \| Equity Securities \| U.S. small cap value
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	8.00%		8.00%
Fair value of plan assets	116,503		139,571
Percentage of Plan Assets	8.00%		10.00%
Pension Plan Asset \| Equity Securities \| U.S. small cap value \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	116,503		139,571
Pension Plan Asset \| Equity Securities \| International
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	20.00%		20.00%
Fair value of plan assets	274,143		295,226
Percentage of Plan Assets	19.00%		21.00%
Pension Plan Asset \| Equity Securities \| International \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			615
Pension Plan Asset \| Equity Securities \| International \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	274,143		294,611
Pension Plan Asset \| Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	40.00%		40.00%
Percentage of Plan Assets	41.00%		35.00%
Pension Plan Asset \| Fixed income securities \| U.S. Treasury and government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	140,057		81,200
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	121,351		76,222
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	18,706		4,978
Pension Plan Asset \| Fixed income securities \| Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	376,939		209,500
Pension Plan Asset \| Fixed income securities \| Corporate bonds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	376,939		209,500
Pension Plan Asset \| Fixed income securities \| Mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,285		116,956
Pension Plan Asset \| Fixed income securities \| Mortgage-backed securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,285		116,956
Pension Plan Asset \| Fixed income securities \| Long duration bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,555		5,177
Pension Plan Asset \| Fixed income securities \| Long duration bonds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,555		5,177
Pension Plan Asset \| Fixed income securities \| Guaranteed annuity contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51,517		52,772
Pension Plan Asset \| Fixed income securities \| Guaranteed annuity contracts \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,987		8,947
Pension Plan Asset \| Fixed income securities \| Guaranteed annuity contracts \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42,530		43,825
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%		100.00%
Fair value of plan assets	512,048		474,718		433,260
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	401,625		370,775
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	103,098		96,183
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	7,325		7,760
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	343,730		353,443
Postretirement Benefit Plan Assets \| Level 1 \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	233,308		249,500
Postretirement Benefit Plan Assets \| Level 1 \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	103,097		96,183
Postretirement Benefit Plan Assets \| Level 1 \| Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,325		7,760
Postretirement Benefit Plan Assets \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	168,318		121,275
Postretirement Benefit Plan Assets \| Level 2 \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	168,317		121,275
Postretirement Benefit Plan Assets \| Level 2 \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1
Postretirement Benefit Plan Assets \| Cash \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	189		689
Postretirement Benefit Plan Assets \| Cash \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	636		3,451
Postretirement Benefit Plan Assets \| Cash \| Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65		27
Postretirement Benefit Plan Assets \| Cash \| Level 1 \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	189		689
Postretirement Benefit Plan Assets \| Cash \| Level 1 \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	636		3,451
Postretirement Benefit Plan Assets \| Cash \| Level 1 \| Life VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65		27
Postretirement Benefit Plan Assets \| Equity Securities \| U.S. large cap \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	9.00%		18.00%
Fair value of plan assets	34,168		72,108
Percentage of Plan Assets	9.00%		19.00%
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	21,966		41,430
Percentage of Plan Assets	21.00%		43.00%
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	4,924		5,527
Percentage of Plan Assets	67.00%		71.00%
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	34,168		72,108
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	21,966		41,430
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	4,924		5,527
Postretirement Benefit Plan Assets \| Equity Securities \| U.S. small cap value \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation			7.00%
Fair value of plan assets			26,574
Percentage of Plan Assets			7.00%
Postretirement Benefit Plan Assets \| Equity Securities \| U.S. small cap value \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	21.00%		21.00%
Fair value of plan assets	21,123
Percentage of Plan Assets	21.00%		0.00%
Postretirement Benefit Plan Assets \| Equity Securities \| U.S. small cap value \| Level 1 \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			26,574
Postretirement Benefit Plan Assets \| Equity Securities \| U.S. small cap value \| Level 1 \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21,122
Postretirement Benefit Plan Assets \| Equity Securities \| U.S. small cap value \| Level 2 \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1
Postretirement Benefit Plan Assets \| Equity Securities \| International \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	11.00%		15.00%
Fair value of plan assets	40,232		55,888
Percentage of Plan Assets	10.00%		15.00%
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	28,611		27,739
Percentage of Plan Assets	28.00%		29.00%
Postretirement Benefit Plan Assets \| Equity Securities \| International \| Level 1 \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40,232		55,888
Postretirement Benefit Plan Assets \| Equity Securities \| International \| Level 1 \| Non-bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28,611		27,739
Postretirement Benefit Plan Assets \| Fixed income securities \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	80.00%		60.00%
Percentage of Plan Assets	81.00%		59.00%
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	30.00%		28.00%
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	33.00%		29.00%
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	155,087		95,010
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	155,087		91,578
Postretirement Benefit Plan Assets \| Fixed income securities \| U.S. Treasury and government bonds \| Level 2 \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			3,432
Postretirement Benefit Plan Assets \| Fixed income securities \| Corporate bonds \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	168,317		117,843
Postretirement Benefit Plan Assets \| Fixed income securities \| Corporate bonds \| Level 2 \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	168,317		117,843
Postretirement Benefit Plan Assets \| Fixed income securities \| Long duration bonds \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,245		2,043
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	3,245		2,043
Postretirement Benefit Plan Assets \| Fixed income securities \| Future and option contracts \| Bargain VEBA
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	387	[1]	620	[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	387	[1]	620	[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	30,762		23,563
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	2,336		2,206
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	30,762		23,563
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	$2,336		$2,206

[1]	Includes cash for margin requirements.

Schedule_of_Significant_Unobse

Schedule of Significant Unobservable Inputs (Details) (Pension Plan Asset, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	$1,383,621	$1,157,697
Actual return on assets	116,363	208,821
Fair value of plan assets ending balance	1,428,160	1,383,621
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	43,825
Purchases, issuances and settlements, net	76,473	-140,184
Fair value of plan assets ending balance	127,351	43,825
Level 3 \| Guaranteed Annuity Contracts And Real Estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	43,825	173,625
Actual return on assets	7,053	10,384
Fair value of plan assets ending balance	$127,351	$43,825

Schedule_of_Rollforward_Change

Schedule of Rollforward Changes in Benefit Obligation and Plan Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Noncurrent liability	($316,368)	($108,542)
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation beginning balance	1,494,132	1,621,244
Service cost	31,773	37,872	34,209
Interest cost	76,652	68,096	70,866
Actuarial (gain) loss	255,762	-180,688
Benefits paid	-111,863	-52,392
Benefit obligation ending balance	1,746,456	1,494,132	1,621,244
Fair value of plan assets beginning balance	1,383,621	1,157,697
Actual return on assets	116,363	208,821
Employer contributions	40,039	69,495
Benefits paid	-111,863	-52,392
Fair value of plan assets ending balance	1,428,160	1,383,621	1,157,697
Funded status ending balance	-318,296	-110,511
Current liability	-1,928	-1,969
Noncurrent liability	-316,368	-108,542
Net amount recognized	-318,296	-110,511
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation beginning balance	561,923	687,082
Service cost	11,058	15,282	14,207
Interest cost	28,605	28,700	31,570
Plan participants' contributions	2,625	2,514
Actuarial (gain) loss	123,342	-148,410
Benefits paid	-26,440	-25,263
Federal subsidy	2,159	2,018
Benefit obligation ending balance	703,272	561,923	687,082
Fair value of plan assets beginning balance	474,718	433,260
Actual return on assets	48,989	36,202
Employer contributions	12,156	28,005
Benefits paid	-26,440	-25,263
Fair value of plan assets ending balance	512,048	474,718	433,260
Funded status ending balance	-191,224	-87,205
Noncurrent asset	1,326	1,271
Current liability	-48	-57
Noncurrent liability	-192,502	-88,419
Net amount recognized	($191,224)	($87,205)

Summary_of_Accumulated_Other_C

Summary of Accumulated Other Comprehensive Income and Regulatory Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$379,743	$145,376
Prior service cost (credit)	3,694	4,418
Net amount recognized	383,437	149,794
Regulatory assets	248,641	90,380
Accumulated other comprehensive income	134,796	59,414
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	119,566	17,632
Prior service cost (credit)	-12,330	-14,519
Net amount recognized	107,236	3,113
Regulatory assets	$107,236	$3,113

Schedule_of_Accumulated_and_Pr

Schedule of Accumulated and Projected Benefit Obligations (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Compensation And Retirement Disclosure [Abstract]
Projected benefit obligation	$1,746,000	$1,494,000
Projected benefit obligation exceeds, fair value of plan assets	1,428,000	1,384,000
Accumulated benefit obligation	1,616,000	43,000
Accumulated benefit obligation exceeds, fair value of plan assets	$1,428,000	$17,000

Schedule_of_Expected_Cash_Flow

Schedule of Expected Cash Flow for Pension and Post Retirement Benefit Plans (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2015	$6,100
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2015	6,632
To Plan Trusts \| Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2015	28,000
To Plan Trusts \| Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2015	26,500
To Plan Participants \| Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2015	1,929
To Plan Participants \| Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions, 2015	$104

Schedule_of_Expected_Benefit_P

Schedule of Expected Benefit Payments (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified	Dec. 31, 2014
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
2015	$63,355
2016	69,673
2017	75,894
2018	82,063
2019	88,635
2020â€”2024	528,913
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
2015	27,897
2016	30,672
2017	33,518
2018	36,502
2019	39,172
2020â€”2024	226,602
Expected Federal Subsidy Payments \| Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
2015	2,113
2016	2,295
2017	2,486
2018	2,678
2019	2,892
2020â€”2024	$18,220

Schedule_of_Pension_and_Post_R

Schedule of Pension and Post Retirement Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Benefit Obligations \| Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations, Discount rate	4.24%	5.12%	4.17%
Weighted average assumptions used to determine benefit obligations, Rate of compensation increase	3.12%	3.15%	3.19%
Benefit Obligations \| Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine benefit obligations, Discount rate	4.24%	5.10%	4.16%
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	6.75%	7.00%	7.25%
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	2021	2019	2019
Net Periodic Costs \| Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine net periodic cost, Discount rate	5.12%	4.17%	5.02%
Weighted average assumptions used to determine net periodic cost, Expected return on plan assets	6.91%	7.49%	7.75%
Weighted average assumptions used to determine net periodic cost, Rate of compensation increase	3.15%	3.19%	3.25%
Net Periodic Costs \| Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Weighted average assumptions used to determine net periodic cost, Discount rate	5.10%	4.16%	5.05%
Weighted average assumptions used to determine net periodic cost, Expected return on plan assets	5.87%	6.99%	7.41%
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	7.00%	7.25%	7.50%
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	2019	2019	2019

Schedule_of_Effect_of_One_Perc

Schedule of Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Effect on total of service and interest cost components, One - Percentage - Point Increase	$5,943
Effect on other postretirement benefit obligation, One - Percentage - Point Increase	105,967
Effect on total of service and interest cost components, One - Percentage - Point Decrease	-4,887
Effect on other postretirement benefit obligation One - Percentage - Point Decrease	($86,179)

Schedule_of_Net_Periodic_Benef

Schedule of Net Periodic Benefit Cost Components (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service credit (cost)	($166)	($174)	($176)
Current year actuarial (gain) loss	46,119	-73,472	26,425
Amortization of actuarial gain (loss)	31	-8,911	-7,301
Total recognized in other comprehensive income	45,984	-82,557	18,948
Total recognized in net periodic benefit cost and comprehensive income	60,164	-27,124	82,245
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Service cost	31,773	37,872	34,209
Interest cost	76,652	68,096	70,866
Expected return on plan assets	-94,838	-88,429	-79,272
Prior service cost (credit)	724	724	723
Actuarial (gain) loss	-131	37,170	29,636
Settlement loss			7,135
Net periodic pension benefit cost	14,180	55,433	63,297
Other Postretirement Benefit Cost
Defined Benefit Plan Disclosure [Line Items]
Service cost	11,058	15,282	14,207
Interest cost	28,605	28,700	31,570
Expected return on plan assets	-27,500	-30,285	-28,711
Prior service cost (credit)	-81	-2,189	-1,915
Actuarial (gain) loss	-2,189	11,128	9,537
Other			-696
Net periodic pension benefit cost	$9,893	$22,636	$23,992

Schedule_of_Estimated_Amounts_

Schedule of Estimated Amounts Amortized Accumulated Other Comprehensive Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Pension Plan Asset
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$25,108
Prior service cost (credit)	754
Net amount recognized	25,862
Postretirement Benefit Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	5,009
Prior service cost (credit)	-2,189
Net amount recognized	$2,820

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss Contingencies [Line Items]
Estimated capital expenditures under legal and binding contractual obligations	$217,082,000
Expenses for purchase of water from regulated subsidiaries	124,334,000	114,471,000	115,426,000
Estimated annual commitment related to purchase of water in 2015	55,141,000
Estimated annual commitment related to purchase of water in 2016	50,936,000
Estimated annual commitment related to purchase of water in 2017	44,175,000
Estimated annual commitment related to purchase of water in 2018	43,034,000
Estimated annual commitment related to purchase of water in 2019	43,098,000
Estimated annual commitment related to purchase of water thereafter	441,206,000
Loss contingency, estimate of possible loss	5,000,000
Loss contingency, range of possible loss, maximum	30,100,000
Settlement agreement date	13-Oct-14
Settlement agreement party name	The Utility Workers Union of America
Settlement agreement terms	Among other things, the settlement agreement provides for a new 2014-2018 National Benefits Agreement that will be in effect generally until July 31, 2018. In addition, we agreed to make a $10 million lump-sum payment, to be distributed in accordance with procedures set forth in the settlement agreement among eligible employees represented by the Unions and affected by implementation of our last, best and final offer.
Settlement agreement lump-sum payment	10,000,000
Military Services Agreements
Loss Contingencies [Line Items]
Estimated remaining contract revenue	2,543,778,000
Military Services Agreements \| Minimum
Loss Contingencies [Line Items]
Agreements expiration period	2051
Military Services Agreements \| Maximum
Loss Contingencies [Line Items]
Agreements expiration period	2064
Operations And Maintenance
Loss Contingencies [Line Items]
Estimated remaining contract revenue	$865,803,000
Operations And Maintenance \| Minimum
Loss Contingencies [Line Items]
Agreements expiration period	2015
Operations And Maintenance \| Maximum
Loss Contingencies [Line Items]
Agreements expiration period	2048

Reconciliation_of_Income_Loss_

Reconciliation of Income (Loss) from Continuing Operations, (Loss) from Discontinued Operations and Net Income (Loss) and Weighted Average Common Shares Outstanding for Calculating Basic Net Earnings (Loss) Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Earnings Per Share [Abstract]
Income from continuing operations	$93,946	$156,608	$110,174	$69,113	$61,121	$149,909	$101,369	$58,445	$429,841		$370,844		$373,602
Loss from discontinued operations, net of tax									-6,733		-1,580		-15,532
Net income	93,501	152,185	109,299	68,123	59,693	150,665	101,263	57,643	423,108		369,264		358,070
Less: Distributed earnings to common shareholders									217,253		150,038		214,541
Less: Distributed earnings to participating securities									63		60		86
Undistributed earnings									205,792		219,166		143,443
Undistributed earnings allocated to common shareholders									205,735		219,082		143,385
Undistributed earnings allocated to participating securities									57		84		58
Total income from continuing operations available to common shareholders, basic									429,721		370,700		373,458
Total income available to common shareholders, basic									$422,988		$369,120		$357,926
Weighted-average common shares outstanding, basic									178,888		177,814		176,445
Basic earnings per share:
Income from continuing operations	$0.52	$0.87	$0.62	$0.39	$0.34	$0.84	$0.57	$0.33	$2.40	[1],[2]	$2.08	[1],[2]	$2.12	[1],[2]
Loss from discontinued operations, net of tax									($0.04)	[1],[2]	($0.01)	[1],[2]	($0.09)	[1],[2]
Net income	$0.52	$0.85	$0.61	$0.38	$0.33	$0.85	$0.57	$0.32	$2.36	[1],[2]	$2.08	[1],[2]	$2.03	[1],[2]

[1]	Amounts may not sum due to rounding
[2]	Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.

Reconciliation_of_Income_Loss_1

Reconciliation of Income (Loss) from Continuing Operations, (Loss) from Discontinued Operations and Net Income (Loss) and Weighted Average Common Shares Outstanding for Calculating Diluted Earnings (Loss) Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Earnings Per Share Diluted [Line Items]
Total income from continuing operations available to common shareholders, basic									$429,721		$370,700		$373,458
Loss from discontinued operations, net of tax									-6,733		-1,580		-15,532
Total income available to common shareholders, basic									422,988		369,120		357,926
Undistributed earnings for participating securities									57		84		58
Total income from continuing operations available to common shareholders, diluted									429,778		370,784		373,516
Total income available to common shareholders, diluted									$423,045		$369,204		$357,984
Weighted-average common shares outstanding, basic									178,888		177,814		176,445
Weighted-average common shares outstanding, diluted									179,806		179,056		177,671
Diluted earnings per share:
Income from continuing operations	$0.52	$0.87	$0.61	$0.39	$0.34	$0.84	$0.57	$0.33	$2.39	[1],[2]	$2.07	[1],[2]	$2.10	[1],[2]
Loss from discontinued operations, net of tax									($0.04)	[1],[2]	($0.01)	[1],[2]	($0.09)	[1],[2]
Net income	$0.52	$0.85	$0.61	$0.38	$0.33	$0.84	$0.57	$0.32	$2.35	[1],[2]	$2.06	[1],[2]	$2.01	[1],[2]
Restricted Stock Units
Earnings Per Share Diluted [Line Items]
Restricted stock units									454		510		618
Employee Stock Purchase Plan
Earnings Per Share Diluted [Line Items]
Employee stock purchase plan									1		2		1
Stock Options
Earnings Per Share Diluted [Line Items]
Stock options									463		730		607

[1]	Amounts may not sum due to rounding
[2]	Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.

Potentially_Dilutive_Common_St

Potentially Dilutive Common Stock Equivalents Were Not Included in Earnings (Loss) Per Share Calculations Because They Were Anti-Dilutive (Details)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive common stock equivalents not included in the earnings (loss) per share calculations	323	327	619
Restricted Stock Units Performance Conditions Not Met
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive common stock equivalents not included in the earnings (loss) per share calculations		20	19

Carrying_Amounts_and_Fair_Valu

Carrying Amounts and Fair Values of Financial Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Preferred stock with mandatory redemption requirements, carrying amount	$17,151	$18,827
Long-term debt (excluding capital lease obligations), carrying amount	5,491,341	5,224,492
Preferred stock with mandatory redemption requirements, fair value	22,167	22,795
Long-term debt (excluding capital lease obligations), fair value	6,404,388	5,783,265
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt (excluding capital lease obligations), fair value	2,874,622	2,263,355
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt (excluding capital lease obligations), fair value	1,474,708	1,462,404
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Preferred stock with mandatory redemption requirements, fair value	22,167	22,795
Long-term debt (excluding capital lease obligations), fair value	$2,055,058	$2,057,506

Fair_Value_Measurements_of_Ass

Fair Value Measurements of Assets and Liabilities on Recurring Basis (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Restricted funds	$45,182	$29,259
Rabbi trust investments	11,751	444
Deposits	4,158	1,901
Mark-to-market derivative asset	3,636	4,776
Total assets	64,727	36,380
Deferred compensation obligation	11,765	11,928
Mark-to-market derivative liability	1,012	1,276
Total liabilities	12,777	13,204
Total net assets (liabilities)	51,950	23,176
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Restricted funds	45,182	29,259
Deposits	4,158	1,901
Total assets	49,340	31,160
Total net assets (liabilities)	49,340	31,160
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Rabbi trust investments	11,751	444
Mark-to-market derivative asset	3,636	4,776
Total assets	15,387	5,220
Deferred compensation obligation	11,765	11,928
Mark-to-market derivative liability	1,012	1,276
Total liabilities	12,777	13,204
Total net assets (liabilities)	$2,610	($7,984)

Fair_Values_of_Financial_Instr2

Fair Values of Financial Instruments - Additional Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Restricted investments	$22,366
Goodwill impairment charges	$0	$0	$0

Leases_Additional_Information_

Leases - Additional Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating and Capital Leases [Line Items]
Rental expenses under operating leases	$21,885	$23,351	$27,945
Minimum annual future rental commitment, 2015	14,007
Minimum annual future rental commitment, 2016	11,898
Minimum annual future rental commitment, 2017	10,970
Minimum annual future rental commitment, 2018	9,763
Minimum annual future rental commitment, 2019	9,457
Minimum annual future rental commitment, thereafter	81,617
Capital lease asset	156,819	158,115
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	20 years
Minimum annual future rental commitment, 2015	3,755
Minimum annual future rental commitment, 2016	3,755
Minimum annual future rental commitment, 2017	3,755
Minimum annual future rental commitment, 2018	3,755
Minimum annual future rental commitment, 2019	3,755
Minimum annual future rental commitment, thereafter	$73,318
Utilities
Operating and Capital Leases [Line Items]
Operating leases expiration term, years	40 years

Segment_Information_Additional

Segment Information - Additional Information (Details)	12 Months Ended
	Dec. 31, 2014
	Segment
Segment Reporting [Abstract]
Number of Operating Segments	2
Segment Reporting, Additional Information about Entity's Reportable Segments	The Regulated Businesses segment includes the Companyâ€™s 18 utility subsidiaries in continuing operations that provide water and wastewater services to customers in 16 U.S. states.

Summarized_Segment_Information

Summarized Segment Information (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net operating revenues	$731,378	$846,169	$754,778	$679,003	$706,242	$822,190	$718,565	$631,939	$3,011,328	$2,878,936	$2,853,926
Depreciation and amortization									424,084	406,717	380,402
Total operating expenses, net									2,008,752	1,930,620	1,929,822
Income from continuing operations before income taxes									709,814	607,937	630,389
Total assets	16,130,956				15,088,142				16,130,956	15,088,142	14,718,976
Capital expenditures									956,119	980,252	928,574
Capital expenditures of discontinued operations (included in capital expenditures above)									12	517	3,589
Assets of discontinued operations (included in total assets above)					7,761					7,761	7,646
Operating Segments \| Regulated Businesses
Segment Reporting Information [Line Items]
Net operating revenues									2,674,329	2,593,918	2,564,434
Depreciation and amortization									394,097	375,939	349,629
Total operating expenses, net									1,725,651	1,700,052	1,685,734
Income from continuing operations before income taxes									707,449	654,834	649,117
Total assets	14,342,837				13,447,696				14,342,837	13,447,696	12,680,856
Capital expenditures									946,306	973,301	921,500
Capital expenditures of discontinued operations (included in capital expenditures above)											2,884
Operating Segments \| Market-Based Operations
Segment Reporting Information [Line Items]
Net operating revenues									354,679	302,541	307,366
Depreciation and amortization									5,790	6,012	5,560
Total operating expenses, net									299,549	252,302	266,005
Income from continuing operations before income taxes									57,539	53,104	44,948
Total assets	314,253				286,048				314,253	286,048	260,255
Capital expenditures									9,813	6,951	7,074
Capital expenditures of discontinued operations (included in capital expenditures above)									12	517	705
Assets of discontinued operations (included in total assets above)					7,761					7,761	7,646
Other
Segment Reporting Information [Line Items]
Net operating revenues									-17,680	-17,523	-17,874
Depreciation and amortization									24,197	24,766	25,213
Total operating expenses, net									-16,448	-21,734	-21,917
Income from continuing operations before income taxes									-55,174	-100,001	-63,676
Total assets	$1,473,866				$1,354,398				$1,473,866	$1,354,398	$1,777,865

Schedule_Of_Unaudited_Quarterl

Schedule Of Unaudited Quarterly Data (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Net operating revenues	$731,378	$846,169	$754,778	$679,003	$706,242	$822,190	$718,565	$631,939	$3,011,328		$2,878,936		$2,853,926
Operating income	223,061	337,285	254,788	187,442	217,795	323,166	242,031	165,324	1,002,576		948,316		924,104
Income from continuing operations	93,946	156,608	110,174	69,113	61,121	149,909	101,369	58,445	429,841		370,844		373,602
Net income	$93,501	$152,185	$109,299	$68,123	$59,693	$150,665	$101,263	$57,643	$423,108		$369,264		$358,070
Basic earnings per common share:
Income from continuing operations	$0.52	$0.87	$0.62	$0.39	$0.34	$0.84	$0.57	$0.33	$2.40	[1],[2]	$2.08	[1],[2]	$2.12	[1],[2]
Net income	$0.52	$0.85	$0.61	$0.38	$0.33	$0.85	$0.57	$0.32	$2.36	[1],[2]	$2.08	[1],[2]	$2.03	[1],[2]
Diluted earnings per common share:
Income from continuing operations	$0.52	$0.87	$0.61	$0.39	$0.34	$0.84	$0.57	$0.33	$2.39	[1],[2]	$2.07	[1],[2]	$2.10	[1],[2]
Net income	$0.52	$0.85	$0.61	$0.38	$0.33	$0.84	$0.57	$0.32	$2.35	[1],[2]	$2.06	[1],[2]	$2.01	[1],[2]

[1]	Amounts may not sum due to rounding
[2]	Earnings per share amounts are computed independently for income from continuing operations, loss from discontinued operations and net income. As a result, the sum of per-share amounts from continuing operations and discontinued operations may not equal the total per-share amount for net income.