Condensed Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating Revenues:
Natural gas sales	$ 33,009	$ 19,937	$ 48,104	$ 36,230
Natural gas transportation	365,246	338,375	727,811	696,543
Natural gas storage	33,935	34,135	68,824	54,057
Other	312	570	1,479	2,053
Total operating revenues	432,502	393,017	846,218	788,883
Operating Costs and Expenses:
Cost of natural gas sales	33,009	19,937	48,104	36,230
Cost of natural gas transportation	4,447	4,741	9,454	10,812
Operation and maintenance	82,100	73,836	154,813	142,059
Administrative and general	44,794	37,866	88,910	85,393
Depreciation and amortization	79,064	76,670	156,542	154,355
Taxes - other than income taxes	16,890	15,169	33,798	30,570
Other expense, net	14,415	17,156	29,637	28,647
Total operating costs and expenses	274,719	245,375	521,258	488,066
Operating Income	157,783	147,642	324,960	300,817
Other (Income) and Other Expenses:
Interest expense	37,236	37,817	74,493	76,639
Allowance for equity and borrowed funds used during construction (AFUDC)	(25,419)	(15,461)	(48,449)	(25,734)
Equity in earnings of unconsolidated affiliates	(1,389)	(1,432)	(2,410)	(2,992)
Miscellaneous other (income) expenses, net	(4,313)	(1,122)	(5,198)	346
Total other (income) and other expenses	6,115	19,802	18,436	48,259
Net Income	151,668	127,840	306,524	252,558
Other comprehensive income (loss):
Equity interest in unrealized gain (loss) on interest rate hedges (includes $22 and $46 for the three months ended and $ 37 and $99 for the six months ended June 30, 2017 and June 30,2016, respectively, of accumulated other comprehensive income reclassification for equity interest in realized losses on interest rate hedges)	1	(50)	36	(284)
Comprehensive Income	$ 151,669	$ 127,790	$ 306,560	$ 252,274