Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 306,524	$ 252,558
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	156,542	154,355
Allowance for equity funds used during construction (equity AFUDC)	(37,260)	(20,888)
Changes in operating assets and liabilities:
Receivables - affiliates	(33)	(530)
Receivables - trade and other	1,789	16,896
Transportation and exchange gas receivable	(1,282)	(3,277)
Inventories	(20,674)	5,426
Payables - affiliates	4,134	(14,167)
Payables - trade	(1,467)	5,985
Accrued liabilities	(29,703)	39,820
Asset retirement obligations - non-current	19,977	1,598
Asset retirement obligations - removal costs	(1,212)	(2,311)
Other, net	10,578	15,822
Net cash provided by operating activities	407,913	451,287
Cash flows from financing activities:
Proceeds from long-term debt	0	998,250
Retirements of long-term debt	0	(200,000)
Payments for debt issuance costs	(13)	(8,235)
Cash distributions to parent	(210,000)	(260,000)
Cash contributions from parent	110,000	222,000
Net cash provided by financing activities	(100,013)	752,015
Cash flows from investing activities:
Property, plant and equipment additions, net of equity AFUDC	(740,079)	(572,667)
Contributions and advances for construction costs	194,108	115,931
Disposal of property, plant and equipment, net	(20,843)	(398)
Advances to affiliate, net	270,641	(731,244)
Return of capital from unconsolidated affiliates	2,100	1,448
Purchase of ARO Trust investments	(32,290)	(49,427)
Proceeds from sale of ARO Trust investments	15,263	30,934
Proceeds from insurance	3,200	2,121
Net cash used in investing activities	(307,900)	(1,203,302)
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	(807,408)	(596,253)
Changes in related accounts payable and accrued liabilities	67,329	23,586
Property, plant and equipment additions, net of equity AFUDC	$ (740,079)	$ (572,667)