Condensed Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues [Abstract]
Natural gas sales	$ 19,654	$ 24,086
Natural gas transportation	566,006	534,160
Natural gas storage	38,374	36,085
Other	3,334	2,762
Total operating revenues	627,368	597,093
Operating Costs and Expenses:
Cost of natural gas sales	19,654	24,086
Cost of natural gas transportation	13,396	14,635
Operation and maintenance	80,689	83,448
Administrative and general	42,171	48,151
Depreciation and amortization	113,635	104,623
Taxes - other than income taxes	22,437	20,277
Regulatory credit resulting from Tax Reform	(7,688)	(1,749)
Other expense, net	3,290	13,349
Total operating costs and expenses	287,584	306,820
Operating Income	339,784	290,273
Other (Income) and Other Expenses:
Interest expense	73,109	71,091
Allowance for equity and borrowed funds used during construction (AFUDC)	(10,953)	(8,714)
Equity in earnings losses of unconsolidated affiliates	0	(771)
Miscellaneous other (income) expenses, net	(356)	(1,035)
Total other (income) and other expenses	61,800	60,571
Net Income	277,984	229,702
Other comprehensive loss
Equity interest in unrealized gain (loss) on interest rate hedges (includes $(78) for the three months ended March 31, 2019 of accumulated other comprehensive income reclassification for equity interest in realized gains on interest rate hedges)	0	(230)
Comprehensive Income	$ 277,984	$ 229,472