Condensed Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues [Abstract]
Natural gas sales	$ 24,086	$ 25,251
Natural gas transportation	534,160	426,579
Natural gas storage	36,085	34,767
Other	2,762	2,639
Total operating revenues	597,093	489,236
Operating Costs and Expenses:
Cost of natural gas sales	24,086	25,251
Cost of natural gas transportation	14,635	13,074
Operation and maintenance	83,448	87,016
Administrative and general	48,151	46,381
Depreciation and amortization	104,623	83,224
Taxes - other than income taxes	20,277	18,438
Regulatory credit resulting from Tax Reform	(1,749)	0
Other expense, net	13,349	17,841
Total operating costs and expenses	306,820	291,225
Operating Income	290,273	198,011
Other (Income) and Other Expenses:
Interest expense	71,091	45,074
Allowance for equity and borrowed funds used during construction (AFUDC)	(8,714)	(26,608)
Equity in (earnings) losses of unconsolidated affiliates	(771)	1,590
Miscellaneous other (income) expenses, net	(1,035)	(1,961)
Total other (income) and other expenses	60,571	18,095
Net Income	229,702	179,916
Other comprehensive income (loss):
Equity interest in unrealized gain (loss) on interest rate hedges (includes $(78) for 2019 and $6 for 2018, of accumulated other comprehensive income reclassification for equity interest in realized losses (gains) on interest rate hedges)	(230)	405
Comprehensive Income	$ 229,472	$ 180,321