STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities
Net income	$ 97,781	$ 79,828
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	106,490	98,592
Deferred income taxes	59,771	19,384
Share-based compensation expense	9,341	3,863
Provision for doubtful accounts	3,521	2,951
Changes in assets and liabilities:
Accounts receivable	107,762	220,392
Materials and supplies	3,227	(5,889)
Income tax receivable	31,925	20,075
Natural gas in storage	(2,077)	25,388
Asset removal costs	(40,715)	(33,744)
Accounts payable	(32,923)	(104,948)
Accrued interest	(11,182)	(11,225)
Accrued taxes other than income	2,670	(4,313)
Accrued liabilities	(13,658)	(8,019)
Customer deposits	100	(1,672)
Regulatory assets and liabilities	(18,726)	64,368
Other assets and liabilities	(21,877)	(15,493)
Cash provided by operating activities	281,430	349,538
Investing activities
Capital expenditures	(231,336)	(199,678)
Other	492	0
Cash used in investing activities	(230,844)	(199,678)
Financing activities
Borrowings (repayments) on notes payable, net	28,500	(42,000)
Repurchase of common stock	(24,066)	(24,122)
Issuance of common stock	1,983	4,471
Dividends paid	(54,923)	(47,178)
Cash provided by (used in) financing activities	(48,506)	(108,829)
Change in cash and cash equivalents	2,080	41,031
Cash and cash equivalents at beginning of period	2,433	11,943
Cash and cash equivalents at end of period	$ 4,513	$ 52,974