Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 124,718	$ 128,818
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	77,685	66,305
Allowance for equity funds used during construction (equity AFUDC)	(8,135)	(11,095)
Changes in operating assets and liabilities:
Receivables - affiliates	449	(345)
Receivables - trade and other	15,720	(3,080)
Transportation and exchange gas receivable	722	421
Inventories	(7,360)	16,474
Payables - affiliates	(5,407)	(6,099)
Payables - trade	(4,185)	(21,121)
Accrued liabilities	4,791	(22,066)
Asset retirement obligation removal costs	(990)	(331)
Other, net	25,343	22,389
Net cash provided by operating activities	223,351	170,270
Cash flows from financing activities:
Proceeds from long-term debt	998,250	0
Payments for debt issuance costs	(8,235)	0
Cash distributions to parent	(175,000)	(123,000)
Cash contributions from parent	112,000	158,000
Other, net	0	(18,287)
Net cash provided by financing activities	927,015	16,713
Cash flows from investing activities:
Property, plant and equipment additions, net of equity AFUDC	(230,968)	(291,162)
Contributions and advances for construction costs	57,196	13,655
Disposal of property, plant and equipment, net	(349)	(126)
Advances to affiliate, net	(964,646)	101,661
Return of capital from unconsolidated affiliates	883	553
Purchase of ARO Trust investments	(33,321)	(29,492)
Proceeds from sale of ARO Trust investments	18,718	17,277
Proceeds from insurance	2,121	0
Other, net	0	623
Net cash used in investing activities	(1,150,366)	(187,011)
Increase (decrease) in cash	0	(28)
Cash at beginning of period	0	173
Cash at end of period	0	145
Increase to property, plant and equipment, net of equity AFUDC	(264,841)	(273,923)
Changes in related accounts payable and accrued liabilities	33,873	(17,239)
Property, plant and equipment additions, net of equity AFUDC	$ (230,968)	$ (291,162)