Consolidated Statments of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net income	$ 48,675	$ 45,017	$ 56,738
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	65,203	63,182	63,322
Amortization of debt premium and expenses	871	825	797
Changes in deferred income taxes	26,818	24,393	34,125
Change in value of life insurance contracts	(1,026)	218	(994)
Stock-based compensation	2,849	2,578	2,195
Loss (gain) on sale of non-utility property	146	(315)	(51)
Write-off of capital costs	3,221	0	0
Changes in operating assets and liabilities:
Receivables	(343)	1,855	4,983
Unbilled revenue	(2,047)	559	(6,706)
Taxes, prepaid expenses, and other assets	1,276	(2,366)	(4,160)
Accounts payable	3,839	(819)	(1,370)
Other current liabilities	4,056	(1,106)	(5,428)
Other changes in noncurrent assets and liabilities	6,162	10,610	(15,318)
Net cash provided by operating activities	159,700	144,631	128,133
Investing activities:
Utility plant expenditures	(228,938)	(176,833)	(132,015)
Proceeds from sale of non-utility assets	395	319	57
Life insurance benefits	495	0	0
Purchase of life insurance	(2,857)	(2,032)	(3,207)
Change in restricted cash	66	288	396
Net cash used in investing activities	(230,839)	(178,258)	(134,769)
Financing activities:
Short-term borrowings net of expenses of $0 for 2016, $1,197 for 2015, and $0 for 2014	145,100	94,303	117,300
Repayment of short-term borrowings	(81,615)	(141,000)	(85,000)
Issuance of long-term debt, net of expenses of $177 for 2016, $707 for 2015, and $0 for 2014	49,823	99,343	497
Advances and contributions in aid of construction	21,448	16,026	12,329
Refunds of advances for construction	(6,885)	(6,726)	(6,641)
Retirement of long-term debt	(6,996)	(7,003)	(8,705)
Dividends paid	(33,081)	(32,066)	(31,063)
Net cash provided by (used in) financing activities	87,794	22,877	(1,283)
Change in cash and cash equivalents	16,655	(10,750)	(7,919)
Cash and cash equivalents at beginning of year	8,837	19,587	27,506
Cash and cash equivalents at end of year	25,492	8,837	19,587
Cash paid (received) during the year for:
Interest (net of amounts capitalized)	28,038	25,345	21,722
Income tax refunds	0	0	(6,000)
Supplemental disclosure of investing and financing non-cash activities:
Accrued payables for investments in utility plant	27,150	21,546	15,621
Utility plant contributed by developers	16,824	7,383	11,556
Litigation proceeds for MTBE contamination reclassified from other long-term liabilities to Capital	$ 484	$ 332	$ 0