STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Document Fiscal Year Focus	2017
Operating activities
Net income	$ 97,079	$ 85,044
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	74,870	70,249
Deferred income taxes	50,308	36,031
Share-based compensation expense	4,951	7,451
Provision for doubtful accounts	3,501	2,757
Changes in assets and liabilities:
Accounts receivable	135,165	98,321
Materials and supplies	(2,792)	707
Natural gas in storage	10,436	38,412
Asset removal costs	(22,837)	(27,672)
Accounts payable	(68,992)	(42,897)
Accrued interest	104	53
Accrued taxes other than income	(9,009)	(5,573)
Accrued liabilities	(6,729)	(16,156)
Customer deposits	(686)	1,113
Regulatory assets and liabilities	19,782	(2,966)
Other assets and liabilities	(5,880)	31,341
Cash provided by operating activities	279,271	276,215
Investing activities
Capital expenditures	(154,666)	(144,760)
Other	477	492
Cash used in investing activities	(154,189)	(144,268)
Financing activities
Repayments of notes payable, net	(66,000)	(12,500)
Repurchase of common stock	(17,512)	(24,066)
Proceeds from Issuance of Common Stock	2,208	1,983
Dividends paid	(44,042)	(36,638)
Tax withholdings related to net share settlements of stock compensation	(9,286)	(8,902)
Cash used in financing activities	(134,632)	(80,123)
Change in cash and cash equivalents	(9,550)	51,824
Cash and cash equivalents at beginning of period	14,663	2,433
Cash and cash equivalents at end of period	$ 5,113	$ 54,257