Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income	$ 63,116	$ 65,584	$ 72,940
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	91,288	85,707	78,592
Amortization of debt premium and expenses	744	1,099	920
Changes in normalized deferred income taxes	15,346	20,909	21,087
Change in value of life insurance contracts	(5,104)	2,334	(3,058)
Allowance for equity funds used during construction	(6,685)	(3,954)	(3,750)
Stock-based compensation	6,731	3,141	3,118
Gain on sale of non-utility properties	(28)	(50)	(663)
Write-off of capital costs	698	410	1,293
Changes in operating assets and liabilities:
Receivables	(4,580)	20,422	(31,871)
Unbilled revenue	(1,452)	(3,671)	(4,528)
Taxes, prepaid expenses, and other assets	(3,545)	(587)	(3,718)
Accounts payable	10,719	4,701	1,564
Other current liabilities	1,282	(4,382)	2,164
Other changes in noncurrent assets and liabilities	264	(12,644)	13,752
Net cash provided by operating activities	168,794	179,019	147,842
Investing activities:
Utility plant expenditures	(273,770)	(271,707)	(259,194)
Proceeds from sale of non-utility assets	28	59	666
TCP settlement proceeds	0	0	56,004
Life insurance benefits	0	3,491	1,558
Purchase of life insurance	(2,216)	(4,925)	(5,605)
Net cash used in investing activities	(275,958)	(273,082)	(206,571)
Financing activities:
Short-term borrowings	260,000	151,000	265,000
Repayment of short-term borrowings	(150,000)	(361,000)	(87,000)
Issuance of long-term debt, net of debt issuance costs of $1,796 for 2019, $617 for 2018, $0 for 2017	398,204	299,383	0
Advances and contributions in aid of construction	27,774	18,612	21,369
Refunds of advances for construction	(7,566)	(7,297)	(8,378)
Retirement of long-term debt	(405,568)	(16,532)	(26,829)
Repurchase of common stock	(2,497)	(1,645)	(1,505)
Issuance of common stock	20,423	0	0
Dividends paid	(38,023)	(36,043)	(34,563)
Net cash provided by financing activities	102,747	46,478	128,094
Change in cash, cash equivalents, and restricted cash	(4,417)	(47,585)	69,365
Cash, cash equivalents, and restricted cash at beginning of year	47,715	95,300	25,935
Cash, cash equivalents, and restricted cash at end of year	43,298	47,715	95,300
Cash paid (received) during the year for:
Interest (net of amounts capitalized)	40,980	35,941	32,223
Income tax refunds	0	0	(1,697)
Supplemental disclosure of investing and financing non-cash activities:
Accrued payables for investments in utility plant	40,794	38,807	41,017
Utility plant contributed by developers	16,288	20,609	19,898
Litigation proceeds for TCP and MTBE contamination reclassified from liability to depreciable plant and equipment	$ 13,968	$ 32,315	$ 2,420