Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 440,856	$ 384,471
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	239,368	231,110
Allowance for equity funds used during construction (equity AFUDC)	(53,867)	(37,285)
Changes in operating assets and liabilities:
Receivables - affiliates	163	341
Receivables - trade and other	(2,156)	17,045
Transportation and exchange gas receivable	883	(216)
Inventories	7,524	13,617
Payables - affiliates	(5,972)	(23,340)
Payables - trade	(28,536)	6,041
Accrued liabilities	(41,137)	61,484
Asset retirement obligations - non-current	45,629	3,761
Asset retirement obligations - removal costs	(1,708)	(2,688)
Deferred revenue	(2,142)	0
Other, net	(4,691)	23,451
Net cash provided by operating activities	594,214	677,792
Cash flows from financing activities:
Proceeds from long-term debt	0	998,250
Retirements of long-term debt	0	(200,000)
Payments on other financing obligation	(241)	0
Payments for debt issuance costs	(13)	(8,235)
Cash distributions to parent	(330,000)	(350,000)
Cash contributions from parent	110,000	372,000
Net cash provided by financing activities	(220,254)	812,015
Cash flows from investing activities:
Property, plant and equipment additions, net of equity AFUDC	(1,089,917)	(906,105)
Contributions and advances for construction costs	252,249	157,545
Disposal of property, plant and equipment, net	(33,281)	(4,439)
Advances to affiliate, net	512,634	(718,279)
Return of capital from unconsolidated affiliates	2,729	2,106
Purchase of ARO Trust investments	(46,709)	(61,086)
Proceeds from sale of ARO Trust investments	27,520	38,330
Proceeds from insurance	3,200	2,121
Other, net	2,385	0
Net cash used in investing activities	(373,960)	(1,489,807)
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	(1,154,317)	(907,023)
Changes in related accounts payable and accrued liabilities	64,400	918
Property, plant and equipment additions, net of equity AFUDC	$ (1,089,917)	$ (906,105)