Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Revenues:
Natural gas sales	$ 121,397	$ 113,488	$ 65,120
Natural gas transportation	1,166,244	1,094,807	1,022,990
Natural gas storage	140,344	143,047	140,390
Other	5,152	4,990	5,601
Total operating revenues	1,433,137	1,356,332	1,234,101
Operating Costs and Expenses:
Cost of natural gas sales	121,397	113,488	65,120
Cost of natural gas transportation	31,629	24,936	31,815
Operation and maintenance	271,603	264,631	299,734
Administrative and general	183,760	182,352	174,610
Depreciation and amortization	270,181	265,273	266,445
Taxes - other than income taxes	44,521	43,898	45,086
Other expense, net	37,208	32,606	21,230
Total operating costs and expenses	960,299	927,184	904,040
Operating Income	472,838	429,148	330,061
Other (Income) and Other Expenses:
Interest expense - affiliate	70	190	309
Interest expense - other	84,917	84,000	88,766
Interest income - affiliate	(49)	(45)	(35)
Interest income - other	(1,782)	(2,068)	(2,351)
Allowance for equity and borrowed funds used during construction (AFUDC)	(25,046)	(18,595)	(19,257)
Equity in earnings of unconsolidated affiliates	(5,783)	(5,678)	(7,458)
Miscellaneous other (income) expenses, net	(2,373)	(2,682)	(2,379)
Total other (income) and other expenses	49,954	55,122	57,595
Net Income	422,884	374,026	272,466
Other comprehensive income (loss):
Equity interest in unrealized gain (loss) on interest rate hedges (includes $344, $330, and $220 for the years ended December 31, 2014, 2013, and 2012, respectively, of accumulated other comprehensive income reclassification for equity interest in realized losses on interest rate hedges)	143	464	(376)
Comprehensive Income	$ 423,027	$ 374,490	$ 272,090