STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities
Net income	$ 64,743	$ 60,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	34,684	31,630
Deferred income taxes	16,113	10,460
Share-based compensation expense	4,101	2,484
Provision for doubtful accounts	1,384	896
Changes in assets and liabilities:
Accounts receivable	19,801	17,003
Materials and supplies	3,617	949
Income tax receivable	38,877	38,210
Natural gas in storage	61,600	104,023
Asset removal costs	(14,171)	(8,168)
Accounts payable	(40,060)	(53,777)
Accrued interest	(11,219)	(11,237)
Accrued taxes other than income	535	3,117
Accrued liabilities	(16,470)	(12,371)
Customer deposits	2,098	853
Regulatory assets and liabilities	(593)	63,434
Other assets and liabilities	14,999	(6,797)
Cash provided by operating activities	180,039	241,090
Investing activities
Capital expenditures	(75,261)	(54,914)
Other	392	0
Cash used in investing activities	(74,869)	(54,914)
Financing activities
Repayments of notes payable, net	(12,500)	(42,000)
Repurchase of common stock	(24,066)	0
Issuance of common stock	0	2,156
Dividends paid	(18,380)	(15,773)
Cash used in financing activities	(54,946)	(55,617)
Change in cash and cash equivalents	50,224	130,559
Cash and cash equivalents at beginning of period	2,433	11,943
Cash and cash equivalents at end of period	$ 52,657	$ 142,502