Segment Information Information By Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 523,526	$ 495,491	$ 482,175	$ 447,536	$ 523,335	$ 504,063	$ 579,140	$ 571,640	$ 1,948,728	$ 2,178,178	$ 2,434,124
Gross profit	164,738	150,084	159,588	140,123	163,500	171,797	196,745	183,105	614,533	715,147	746,458
Operating income (loss)									(135,181)	151,126	(459,183)
Total other income (expense)									(13,073)	(14,907)	(42,583)
Income (loss) before income taxes									(148,254)	136,219	(501,766)
Depreciation and amortization									98,845	109,471	129,466
Electricity Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues									836,553	1,024,340	1,239,428
Gross profit									218,913	295,005	323,632
Operating income (loss)									(235,908)	24,812	(218,284)
Depreciation and amortization									46,535	52,113	62,860
Gas Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues									570,297	627,193	672,999
Gross profit									207,915	235,391	254,943
Operating income (loss)									83,882	110,557	105,453
Depreciation and amortization									27,266	29,968	34,275
Water Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues									541,878	526,645	521,697
Gross profit									187,705	184,751	167,883
Operating income (loss)									63,252	59,210	(303,772)
Depreciation and amortization									24,797	27,324	32,313
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)									(46,407)	(43,453)	(42,580)
Depreciation and amortization									$ 247	$ 66	$ 18