Consolidated Statments of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income	$ 65,584	$ 72,940	$ 48,675
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	85,707	78,592	65,203
Amortization of debt premium and expenses	1,099	920	871
Changes in normalized deferred income taxes	20,909	21,087	26,818
Change in value of life insurance contracts	2,334	(3,058)	(1,026)
Allowance for equity funds used during construction	(3,954)	(3,750)	0
Stock-based compensation	3,141	3,118	2,849
(Gain) loss on sale of non-utility property	(50)	(663)	146
Write-off of capital costs	410	1,293	3,221
Changes in operating assets and liabilities:
Receivables	20,422	(31,871)	(343)
Unbilled revenue	(3,671)	(4,528)	(2,047)
Taxes, prepaid expenses, and other assets	(587)	(3,718)	1,276
Accounts payable	4,701	1,564	3,839
Other current liabilities	(4,382)	2,164	4,056
Other changes in noncurrent assets and liabilities	(12,644)	13,752	6,906
Net cash provided by operating activities	179,019	147,842	160,444
Investing activities:
Utility plant expenditures	(271,707)	(259,194)	(228,938)
Proceeds from sale of non-utility assets	59	666	395
TCP settlement proceeds	0	56,004	0
Life insurance benefits	3,491	1,558	495
Purchase of life insurance	(4,925)	(5,605)	(2,857)
Net cash used in investing activities	(273,082)	(206,571)	(230,905)
Financing activities:
Short-term borrowings	151,000	265,000	145,100
Repayment of short-term borrowings	(361,000)	(87,000)	(81,615)
Issuance of long-term debt, net of expenses of $617 for 2018, $0 for 2017, $177 for 2016	299,383	0	49,823
Advances and contributions in aid of construction	18,612	21,369	21,448
Refunds of advances for construction	(7,297)	(8,378)	(6,885)
Retirement of long-term debt	(16,532)	(26,829)	(6,996)
Repurchase of common stock	(1,645)	(1,505)	(744)
Dividends paid	(36,043)	(34,563)	(33,081)
Net cash provided by financing activities	46,478	128,094	87,050
Change in cash, cash equivalents, and restricted cash	(47,585)	69,365	16,589
Cash, cash equivalents, and restricted cash at beginning of year	95,300	25,935	9,346
Cash, cash equivalents, and restricted cash at end of year	47,715	95,300	25,935
Cash paid (received) during the year for:
Interest (net of amounts capitalized)	35,941	32,223	28,038
Income tax refunds	0	(1,697)	0
Supplemental disclosure of investing and financing non-cash activities:
Accrued payables for investments in utility plant	38,807	41,017	27,150
Utility plant contributed by developers	20,609	19,898	16,824
Litigation proceeds for contamination reclassified from liabilities to depreciable plant and equipment	$ 32,315	$ 2,420	$ 484