CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES:
Net Income	$ 58,499	$ 56,567
Items not affecting cash:
Depreciation and depletion	43,755	41,461
Amortization of debt issue costs, discount and deferred hedge gain	1,171	1,201
Stock-based compensation costs	2,496	2,332
Equity portion of allowance for funds used during construction	(618)	(984)
Loss (gain) on disposition of assets	15	(86)
Deferred income taxes	2,143	5,410
Changes in current assets and liabilities:
Accounts receivable	12,012	17,004
Inventories	8,718	6,929
Other current assets	3,258	2,386
Accounts payable	(21,605)	(15,806)
Accrued expenses	41,802	33,306
Regulatory assets	13,208	17,004
Regulatory liabilities	2,205	(7,330)
Other noncurrent assets	(1,505)	(3,301)
Other noncurrent liabilities	7,474	1,108
Cash Provided by Operating Activities	173,028	157,201
INVESTING ACTIVITIES:
Property, plant, and equipment additions	(52,005)	(51,519)
Proceeds from sale of assets	0	76
Cash Used in Investing Activities	(52,005)	(51,443)
FINANCING ACTIVITIES:
Treasury stock activity	1,574	(872)
Dividends on common stock	(26,945)	(25,194)
Line of credit borrowings	578,000	0
Line of credit repayments	(355,000)	0
Repayments of short-term borrowings, net	(319,556)	(71,910)
Financing costs	(225)	(2)
Cash Used in Financing Activities	(122,152)	(97,978)
(Decrease) Increase in Cash, Cash Equivalents, and Restricted Cash	(1,129)	7,780
Cash, Cash Equivalents, and Restricted Cash, beginning of period	12,029	9,505
Cash, Cash Equivalents, and Restricted Cash, end of period	10,900	17,285
Cash paid during the period for:
Income taxes	55	61
Interest	12,172	11,242
Significant non-cash transactions:
Capital expenditures included in accounts payable	$ 7,135	$ 6,788