CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES:
Net Income	$ 56,567	$ 39,867
Items not affecting cash:
Depreciation and depletion	41,461	39,890
Amortization of debt issue costs, discount and deferred hedge gain	1,201	979
Stock-based compensation costs	2,332	2,242
Equity portion of allowance for funds used during construction	(984)	(652)
Gain on disposition of assets	(86)	(55)
Deferred income taxes	5,410	3,077
Changes in current assets and liabilities:
Restricted cash	(426)	(197)
Accounts receivable	17,004	19,427
Inventories	6,929	6,825
Other current assets	2,386	(3,374)
Accounts payable	(15,806)	(11,303)
Accrued expenses	33,306	38,023
Regulatory assets	17,004	10,550
Regulatory liabilities	(7,330)	(2,971)
Other noncurrent assets	(3,301)	(1,485)
Other noncurrent liabilities	1,108	1,293
Cash Provided by Operating Activities	156,775	142,136
INVESTING ACTIVITIES:
Property, plant, and equipment additions	(51,519)	(51,318)
Proceeds from sale of assets	76	51
Cash Used in Investing Activities	(51,443)	(51,267)
FINANCING ACTIVITIES:
Treasury stock activity	(872)	(1,788)
Dividends on common stock	(25,194)	(23,922)
Repayments of short-term borrowings, net	(71,910)	(67,961)
Financing costs	(2)	(151)
Cash Used in Financing Activities	(97,978)	(93,822)
Increase (Decrease) in Cash and Cash Equivalents	7,354	(2,953)
Cash and Cash Equivalents, beginning of period	5,079	11,980
Cash and Cash Equivalents, end of period	12,433	9,027
Cash paid (received) during the period for:
Income taxes	61	(2,948)
Interest	11,242	12,977
Significant non-cash transactions:
Capital expenditures included in accounts payable	$ 6,788	$ 5,805