Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 372,138	$ 306,524
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	172,506	156,542
Allowance for equity funds used during construction (equity AFUDC)	(45,910)	(37,260)
Regulatory credit resulting from Tax Reform (Note 1)	(20,867)	0
Equity in (earnings) losses of unconsolidated affiliates	265	(2,410)
Distribution from unconsolidated affiliates	931	4,848
Changes in operating assets and liabilities:
Receivables - affiliates	300	(33)
Receivables - trade and other	5,053	1,789
Transportation and exchange gas receivable	(4,932)	(1,282)
Inventories	(19,794)	(20,674)
Payables - affiliates	(10,686)	4,134
Payables - trade	(30,052)	(1,467)
Accrued liabilities	15,719	(29,703)
Asset retirement obligations - non-current	23,230	19,977
Asset retirement obligations - removal costs	(4,013)	(1,212)
Deferred revenue	(5,279)	(479)
Other, net	(12,222)	10,719
Net cash provided by operating activities	436,387	410,013
Cash flows from financing activities:
Proceeds from long-term debt	993,440	0
Proceeds from other financing obligations	24,298	0
Retirement of long-term debt	250,000	0
Payments on other financing obligation	(758)	0
Payments for debt issuance costs	(9,208)	(13)
Cash distributions to parent	(190,000)	(210,000)
Cash contributions from parent	340,000	110,000
Net cash provided by financing activities	907,772	(100,013)
Cash flows from investing activities:
Property, plant and equipment additions, net of equity AFUDC	(1,463,600)	(740,079)
Contributions and advances for construction costs	337,874	194,108
Disposal of property, plant and equipment, net	(7,477)	(20,843)
Advances to affiliate, net	(193,886)	270,641
Purchase of ARO Trust investments	(36,807)	(32,290)
Proceeds from sale of ARO Trust investments	19,737	15,263
Proceeds from insurance	0	3,200
Net cash used in investing activities	(1,344,159)	(310,000)
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	(1,434,519)	(807,408)
Changes in related accounts payable and accrued liabilities	(29,081)	67,329
Property, plant and equipment additions, net of equity AFUDC	$ (1,463,600)	$ (740,079)