Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Net income	$ 48,828	$ 37,712	$ 37,656
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	56,866	51,981	45,265
Amortization of debt premium and expenses	1,107	1,082	979
Changes in deferred income taxes	34,133	2,723
Other changes in noncurrent assets and liabilities	(8,490)	611	(1,139)
Change in value of life insurance contracts	(2,504)	1,876	(2,641)
Gain on sale of non-utility property	(84)	(62)	(22)
Changes in operating assets and liabilities:
Receivables	(1,392)	(8,213)	(860)
Unbilled revenue	(326)	(1,143)	(508)
Taxes, prepaid expenses, and other assets	(3,322)	11,823	(2,842)
Accounts payable	879	4,612	220
Other current liabilities	6,219	8,270	(598)
Net adjustments	83,086	73,560	37,854
Net cash provided by operating activities	131,914	111,272	75,510
Investing activities:
Utility plant expenditures	(127,681)	(118,546)	(123,926)
Proceeds from sale of non-utility assets	85	64	34
Purchase of life insurance	(3,294)	(1,744)	(1,891)
Change in restricted cash	1,959	(3,042)	3,169
Net cash used in investing activities	(128,931)	(123,268)	(122,614)
Financing activities:
Short-term borrowings	94,335	23,390	85,750
Repayment of short-term borrowings	(52,000)		(74,000)
Issuance of common stock, net of expenses		965	912
Issuance of long-term debt, net of expenses	124	178	106,173
Advances and contributions in aid of construction	6,966	7,231	5,313
Refunds of advances for construction	(7,397)	(6,205)	(6,188)
Retirement of long-term debt	(7,037)	(2,963)	(13,692)
Dividends paid	(26,387)	(25,674)	(24,753)
Net cash provided by (used in) financing activities	8,604	(3,078)	79,515
Change in cash and cash equivalents	11,587	(15,074)	32,411
Cash and cash equivalents at beginning of year	27,203	42,277	9,866
Cash and cash equivalents at end of year	38,790	27,203	42,277
Cash paid (received) during the year for:
Interest (net of amounts capitalized)	27,120	26,998	24,425
Income taxes		10,535	9,815
Income tax refunds	(5,349)	(11,028)
Supplemental disclosure of non-cash activities:
Accrued payables for investments in utility plant	11,048	9,008	6,565
Utility plant contributed by developers	13,630	14,991	31,422
MTBE reclassification from other long-term liabilities to CIAC	4,462	16,735
Capital leases		$ 9,388