CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities
Net income	$ 41,588	$ 43,822
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	45,067	42,722
Change in value of life insurance contracts	(1,147)	(2,244)
Other changes in noncurrent assets and liabilities	13,501	28,411
Changes in operating assets and liabilities:
Receivables	(24,636)	(34,462)
Accounts payable	7,719	13,066
Other current assets	(751)	(2,491)
Other current liabilities	20,558	10,581
Net cash provided by operating activities	101,899	99,405
Investing activities:
Utility plant expenditures	(94,782)	(99,600)
Purchase of life insurance	(3,204)	(3,199)
Restricted cash decrease	1,148	1,553
Net cash (used in) investing activities	(96,838)	(101,246)
Financing activities:
Short-term borrowings	35,315	65,565
Repayment of short-term borrowing	(113,275)	(52,030)
Proceeds from long-term debt	48	123
Repayment of long-term debt	(3,058)	(2,123)
Advances and contributions in aid of construction	7,577	5,491
Refunds of advances for construction	(5,230)	(5,632)
Issuance of common stock	110,688
Common stock issuance cost	(5,088)
Dividends paid	(21,981)	(19,785)
Net cash provided by (used in) financing activities	4,996	(8,391)
Change in cash and cash equivalents	10,057	(10,232)
Cash and cash equivalents at beginning of period	38,790	27,203
Cash and cash equivalents at end of period	48,847	16,971
Supplemental information
Cash paid for interest (net of amounts capitalized)	15,141	13,721
Refund for income taxes		(3,498)
Supplemental disclosure of non-cash activities:
Accrued payables for investments in utility plant	11,739	9,654
Utility plant contribution by developers	$ 10,196	$ 11,868