Condensed Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating Revenues:
Natural gas sales	$ 27,282	$ 15,828	$ 87,866	$ 36,691
Natural gas transportation	268,426	251,691	808,002	761,659
Natural gas storage	35,736	34,714	107,243	105,171
Other	811	724	3,085	3,079
Total operating revenues	332,255	302,957	1,006,196	906,600
Operating Costs and Expenses:
Cost of natural gas sales	27,282	15,828	87,866	36,691
Cost of natural gas transportation	3,056	8,104	22,053	27,264
Operation and maintenance	70,294	79,991	194,008	219,518
Administrative and general	43,747	42,443	135,767	131,225
Depreciation and amortization	66,989	66,693	198,148	199,068
Taxes - other than income taxes	11,318	11,133	33,879	33,660
Other (income) expense, net	12,562	7,753	24,750	31,214
Total operating costs and expenses	235,248	231,945	696,471	678,640
Operating Income	97,007	71,012	309,725	227,960
Other (Income) and Other Expenses:
Interest expense	21,416	21,132	62,716	68,518
Allowance for equity and borrowed funds used during construction (AFUDC)	(5,002)	(5,886)	(15,352)	(14,468)
Equity in earnings of unconsolidated affiliates	(1,493)	(2,127)	(4,234)	(5,395)
Miscellaneous other (income) expenses, net	(1,632)	(2,069)	(4,747)	(4,121)
Total other (income) and other expenses	13,289	11,050	38,383	44,534
Net Income	83,718	59,962	271,342	183,426
Equity interest in unrealized gain (loss) on interest rate hedges (includes $83 and $68 for the three months ended and $244 and $145 for the nine months ended September 30, 2013 and September 30, 2012, respectively, of accumulated other comprehensive income reclassification for realized losses on interest rate hedges)	(102)	(283)	404	(441)
Comprehensive Income	$ 83,616	$ 59,679	$ 271,746	$ 182,985