Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net income	$ 56,597	$ 67,103	$ 63,445
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation and amortization including regulatory items	88,801	82,754	71,734
Pension and other postretirement benefit costs, net of contributions	(9,184)	1,973	(1,888)
Deferred income taxes and unamortized investment tax credit, net	36,617	41,693	28,272
Allowance for equity funds used during construction	(4,850)	(6,420)	(3,853)
Stock compensation expense	4,082	4,057	2,984
Other	(625)
Loss on plant disallowance		86	2,409
Reverse gain on sale of assets		44	1,236
Non-cash (gain)/loss on derivatives	6,994	1,245	14
Cash flows impacted by changes in:
Accounts receivable and accrued unbilled revenues	16,514	(24,174)	(14,312)
Fuel, materials and supplies	(3,151)	(8,121)	10,891
Prepaid expenses, other current assets and deferred charges	(4,863)	(6,051)	689
Accounts payable and accrued liabilities	(8,630)	1,141	(880)
Asset retirement obligations	(73)	(1,326)	(734)
Interest, taxes accrued and customer deposits	1,111	1,411	1,386
Other liabilities and other deferred credits	5,492	(4,192)	(3,942)
Net cash provided by operating activities	184,832	151,223	157,451
Investing activities:
Capital expenditures - regulated	(183,206)	(211,429)	(152,524)
Capital expenditures and other investments - non-regulated	(2,243)	(1,998)	(2,259)
Restricted cash		(1,854)	1,485
Net cash used in investing activities	(185,449)	(215,281)	(153,298)
Financing activities:
Proceeds from first mortgage bonds, net	60,000	60,000	150,000
Long-term debt issuance costs	(818)	(651)	(1,879)
Proceeds from issuance of common stock, net of issuance costs	5,513	7,994	9,546
Redemption of senior notes			(98,000)
Net short-term debt borrowings/(repayments)	(19,000)	40,000	(20,000)
Dividends	(45,430)	(44,381)	(43,006)
Other		(274)	(714)
Net cash provided by financing activities	265	62,688	(4,053)
Net increase (decrease) in cash and cash equivalents	(352)	(1,370)	100
Cash and cash equivalents at beginning of period	2,105	3,475	3,375
Cash and cash equivalents at end of period	1,753	2,105	3,475
Supplemental cash flow information:
Interest paid	42,858	40,127	39,033
Income taxes (refunded) paid, net of refund	(17,256)	23,103	10,584
Supplementary non-cash investing activities:
Change in accrued additions to property, plant and equipment not reported above	(8,924)	$ 9,427	$ 5,420
Capital lease obligations for purchase of new equipment	$ 17