STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net income	$ 76,456	$ 64,743
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	37,019	34,684
Deferred income taxes	37,461	16,113
Share-based compensation expense	2,421	4,101
Provision for doubtful accounts	2,281	1,384
Changes in assets and liabilities:
Accounts receivable	39,508	19,801
Materials and supplies	(204)	3,617
Income tax receivable	1,397	38,877
Natural gas in storage	34,201	61,600
Asset removal costs	(10,387)	(14,171)
Accounts payable	(53,957)	(40,060)
Accrued interest	(11,187)	(11,219)
Accrued taxes other than income	(5,140)	535
Accrued liabilities	(10,457)	(16,470)
Customer deposits	736	2,098
Regulatory assets and liabilities	18,641	(593)
Other assets and liabilities	3,447	23,848
Cash provided by operating activities	162,236	188,888
Investing activities
Capital expenditures	(70,471)	(75,261)
Other	61	392
Cash used in investing activities	(70,410)	(74,869)
Financing activities
Repayments of notes payable, net	(59,600)	(12,500)
Repurchase of common stock	(2,469)	(24,066)
Dividends paid	(22,034)	(18,380)
Tax withholdings related to net share settlements of stock compensation	(9,180)	(8,849)
Cash used in financing activities	(93,283)	(63,795)
Change in cash and cash equivalents	(1,457)	50,224
Cash and cash equivalents at beginning of period	14,663	2,433
Cash and cash equivalents at end of period	$ 13,206	$ 52,657