Consolidated Statements Of Cash Flow (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 109,064	$ 95,117
(Loss) income from discontinued operations	(3,737)	4,404
Income from continuing operations	112,801	90,713
Adjustments to reconcile income from continuing operations to net cash flows from operating activities:
Depreciation and amortization	84,219	86,879
Deferred income taxes	58,495	34,623
Provision for doubtful accounts	3,615	3,475
Stock-based compensation	2,768	3,015
Gain on sale of utility system	(3,946)
Gain on sale of other assets	(475)	(2,294)
Net increase in receivables, inventory and prepayments	(14,001)	(20,634)
Net increase (decrease) in payables, accrued interest, accrued taxes and other accrued liabilities	323	(16,722)
Other	(3,162)	(2,763)
Operating cash flows from continuing operations	240,637	176,292
Operating cash flows from discontinued operations, net	6,466	12,336
Net cash flows from operating activities	247,103	188,628
Cash flows from investing activities: [Abstract]
Property, plant and equipment additions, including allowance for funds used during construction of $5,710 and $3,895	(226,075)	(231,542)
Acquisitions of utility systems and other, net	(6,934)	(1,948)
Additions to funds restricted for construction activity	(135)	(1,051)
Release of funds previously restricted for construction activity	34,644	41,635
Net proceeds from the sale of utility system and other assets	12,628	3,541
Proceeds from note receivable	5,289	1,955
Other	(631)	(5,643)
Investing cash flows used in continuing operations	(181,214)	(193,053)
Investing cash flows used in discontinued operations, net	(2,915)	(5,967)
Net cash flows used in investing activities	(184,129)	(199,020)
Cash flows from financing activities:
Customers' advances and contributions in aid of construction	3,324	5,572
Repayments of customers' advances	(1,577)	(5,199)
Net proceeds of short-term debt	13,310	42,041
Proceeds from long-term debt	24,974	114,313
Repayments of long-term debt	(46,477)	(97,332)
Change in cash overdraft position	(4,122)	(10,173)
Proceeds from issuing common stock	9,401	9,288
Proceeds from exercised stock options	5,835	3,889
Stock-based compensation windfall tax benefits		302
Repurchase of common stock	(1,001)	(744)
Dividends paid on common stock	(64,266)	(59,584)
Financing cash flows (used in) from continuing operations	(60,599)	2,373
Financing cash flows used in discontinued operations, net	(321)	(296)
Net cash flows (used in) from financing activities	(60,920)	2,077
Net increase (decrease) in cash and cash equivalents	2,054	(8,315)
Cash and cash equivalents at beginning of period	5,934	21,869
Cash and cash equivalents at end of period	$ 7,988	$ 13,554