Condensed Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating Revenues:
Natural gas sales	$ 29,873	$ 33,009	$ 55,124	$ 48,104
Natural gas transportation	415,708	365,246	842,286	727,811
Natural gas storage	33,786	33,935	68,553	68,824
Other	2,308	312	4,948	1,479
Total operating revenues	481,675	432,502	970,911	846,218
Operating Costs and Expenses:
Cost of natural gas sales	29,873	33,009	55,124	48,104
Cost of natural gas transportation	8,461	4,447	21,535	9,454
Operation and maintenance	93,659	82,100	180,675	154,813
Administrative and general	46,981	44,794	93,362	88,910
Depreciation and amortization	89,282	79,064	172,506	156,542
Taxes - other than income taxes	17,164	16,890	35,602	33,798
Regulatory credit resulting from Tax Reform (Note 1)	(20,867)	0	(20,867)	0
Other expense, net	12,564	14,415	30,405	29,637
Total operating costs and expenses	277,117	274,719	568,342	521,258
Operating Income	204,558	157,783	402,569	324,960
Other (Income) and Other Expenses:
Interest expense	53,375	37,236	98,449	74,493
Allowance for equity and borrowed funds used during construction (AFUDC)	(34,895)	(25,419)	(61,503)	(48,449)
Equity in (earnings) losses of unconsolidated affiliates	(1,325)	(1,389)	265	(2,410)
Miscellaneous other (income) expenses, net	(4,819)	(4,313)	(6,780)	(5,198)
Total other (income) and other expenses	12,336	6,115	30,431	18,436
Net Income	192,222	151,668	372,138	306,524
Other comprehensive income:
Equity interest in unrealized gain on interest rate hedges (includes $(33) and $22 for the three months ended and $(27) and $37 for the six months ended June 30, 2018 and June 30, 2017, respectively, of accumulated other comprehensive income reclassification for equity interest in realized losses (gains) on interest rate hedges)	119	1	524	36
Comprehensive Income	$ 192,341	$ 151,669	$ 372,662	$ 306,560