Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 179,916	$ 154,856
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	83,224	77,478
Allowance for equity funds used during construction (equity AFUDC)	(19,782)	(18,366)
Equity in (earnings) loss of unconsolidated affiliates	1,590	(1,021)
Distribution from unconsolidated affiliates	429	2,598
Changes in operating assets and liabilities:
Receivables - affiliates	598	(452)
Receivables - trade and other	8,612	6,231
Transportation and exchange gas receivable	275	(1,467)
Inventories	(37,886)	(14,370)
Payables - affiliates	(29,496)	(1,064)
Payables - trade	(52,553)	(11,738)
Accrued liabilities	(13,385)	(71,928)
Asset retirement obligations - non-current	18,400	24,670
Asset retirement obligations - removal costs	(1,199)	(222)
Deferred revenue	(2,638)	0
Other, net	(4,384)	6,593
Net cash provided by operating activities	131,721	151,798
Cash flows from financing activities:
Proceeds from long-term debt	993,440	0
Proceeds from other financing obligations	18,804	0
Payments on other financing obligation	(375)	0
Payments for debt issuance costs	(9,025)	(13)
Cash distributions to parent	(55,000)	(100,000)
Cash contributions from parent	340,000	110,000
Net cash provided by financing activities	1,287,844	9,987
Cash flows from investing activities:
Property, plant and equipment additions, net of equity AFUDC	(737,004)	(374,220)
Contributions and advances for construction costs	188,543	131,874
Disposal of property, plant and equipment, net	(5,241)	(2,131)
Advances to affiliate, net	(854,125)	91,733
Purchase of ARO Trust investments	(15,530)	(22,418)
Proceeds from sale of ARO Trust investments	3,792	10,177
Proceeds from insurance	0	3,200
Net cash used in investing activities	(1,419,565)	(161,785)
Increase (decrease) in cash	0	0
Cash at beginning of period	0	0
Cash at end of period	0	0
Increase to property, plant and equipment, net of equity AFUDC	(721,921)	(434,824)
Changes in related accounts payable and accrued liabilities	(15,083)	60,604
Property, plant and equipment additions, net of equity AFUDC	$ (737,004)	$ (374,220)