The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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-Section 45

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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Segment Information Information By Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	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]
Revenues	$ 510,095us-gaap_SalesRevenueNet	$ 496,454us-gaap_SalesRevenueNet	$ 489,353us-gaap_SalesRevenueNet	$ 474,795us-gaap_SalesRevenueNet	$ 523,526us-gaap_SalesRevenueNet	$ 495,491us-gaap_SalesRevenueNet	$ 482,175us-gaap_SalesRevenueNet	$ 447,536us-gaap_SalesRevenueNet	$ 1,970,697us-gaap_SalesRevenueNet	$ 1,948,728us-gaap_SalesRevenueNet	$ 2,178,178us-gaap_SalesRevenueNet
Gross profit	154,787us-gaap_GrossProfit	150,762us-gaap_GrossProfit	163,041us-gaap_GrossProfit	154,535us-gaap_GrossProfit	164,738us-gaap_GrossProfit	150,084us-gaap_GrossProfit	159,588us-gaap_GrossProfit	140,123us-gaap_GrossProfit	623,125us-gaap_GrossProfit	614,533us-gaap_GrossProfit	715,147us-gaap_GrossProfit
Operating income (loss)									3,832us-gaap_OperatingIncomeLoss	(135,181)us-gaap_OperatingIncomeLoss	151,126us-gaap_OperatingIncomeLoss
Total other income (expense)									(18,741)us-gaap_NonoperatingIncomeExpense	(13,073)us-gaap_NonoperatingIncomeExpense	(14,907)us-gaap_NonoperatingIncomeExpense
Income (loss) before income taxes									(14,909)	(148,254)	136,219
Depreciation and amortization									98,463	98,845	109,471
Electricity Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues									794,144	836,553	1,024,340
Gross profit									208,476	218,913	295,005
Operating income (loss)									(72,476)	(235,908)	24,812
Depreciation and amortization									47,886	46,535	52,113
Gas Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues									599,081	570,297	627,193
Gross profit									211,815	207,915	235,391
Operating income (loss)									75,598	83,882	110,557
Depreciation and amortization									26,031	27,266	29,968
Water Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues									577,472	541,878	526,645
Gross profit									202,834	187,705	184,751
Operating income (loss)									71,006	63,252	59,210
Depreciation and amortization									24,259	24,797	27,324
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)									(70,296)	(46,407)	(43,453)
Depreciation and amortization									$ 287	$ 247	$ 66