STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income	$ 140,095	$ 119,030	$ 109,790
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	143,829	133,023	125,722
Deferred income taxes	86,788	63,789	49,935
Share-based compensation expense	11,219	9,187	7,613
Provision for doubtful accounts	5,427	4,520	7,195
Changes in assets and liabilities:
Accounts receivable	(80,028)	105,886	23,044
Materials and supplies	(759)	(5,814)	10,868
Income Tax Receivable	37,480	4,923	(43,800)
Natural gas in storage	16,721	43,147	(19,172)
Asset removal costs	(53,430)	(51,608)	(47,125)
Accounts payable	27,596	(59,635)	(6,881)
Accrued interest	(19)	1	18,743
Accrued taxes other than income	5,322	(7,493)	12,316
Accrued Liabilities	(8,539)	5,451	21,228
Customer deposits	884	322	2,643
Regulatory assets and liabilities	(49,472)	50,658	30,067
Employee benefit obligation	(25,666)	(15,033)	(10,102)
Other assets and liabilities	24,119	(6,147)	(45,421)
Cash provided by operating activities	281,567	394,207	246,663
Investing activities
Capital expenditures	(309,071)	(294,320)	(297,103)
Other	492	0	0
Cash used in investing activities	(308,579)	(294,320)	(297,103)
Financing activities
Borrowings (repayment) on notes payable, net	132,500	(29,500)	42,000
Repurchase of common stock	(24,066)	(24,122)	0
Issuance of debt, net of discounts	0	0	1,199,994
Long-term debt financing costs	0	0	(11,087)
Cash payment to ONEOK upon separation	0	0	(1,130,000)
Issuance of common stock	4,017	7,051	2,001
Dividends paid	(73,209)	(62,826)	(43,696)
Cash provided by financing activities	39,242	(109,397)	59,212
Change in cash and cash equivalents	12,230	(9,510)	8,772
Cash and cash equivalents at beginning of period	2,433	11,943	3,171
Cash and cash equivalents at end of period	14,663	2,433	11,943
Supplemental cash flow information:
Cash paid for interest, net of amounts capitalized	42,129	42,980	21,066
Cash (received) paid for income taxes, net	$ (35,702)	$ (5,423)	$ 44,603