CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Operating Revenues:
Gas transportation	$ 241.2	$ 251.8	$ 773.7	$ 786.6
Parking and lending	8.3	2.2	20.1	8.5
Gas storage	18.3	12.0	57.0	37.5
Other	2.8	2.9	8.5	9.3
Total operating revenues	270.6	268.9	859.3	841.9
Operating Costs and Expenses:
Fuel and gas transportation	18.2	26.7	51.9	78.7
Operation and maintenance	39.4	45.9	119.1	123.1
Administrative and general	24.5	31.1	83.9	101.9
Depreciation and amortization	60.4	55.8	184.8	168.9
Asset impairment	1.1	0.1	8.2	28.6
Net loss (gain) on disposal of operating assets	1.2	(5.3)	(2.6)	(3.9)
Taxes other than income taxes	23.1	22.2	69.2	67.1
Total operating costs and expenses	167.9	176.5	514.5	564.4
Operating income	102.7	92.4	344.8	277.5
Other Deductions (Income):
Interest expense	41.5	37.6	122.0	113.5
Interest expense - affiliates	2.0	2.0	6.0	6.0
Loss on early retirement of debt	0	5.8	0	13.2
Interest income	(0.2)	(0.1)	(0.4)	(0.3)
Miscellaneous other expense (income), net	0.3	(0.2)	0.1	(0.6)
Total other deductions	43.6	45.1	127.7	131.8
Income before income taxes	59.1	47.3	217.1	145.7
Income taxes	0.1	0.1	0.4	0.3
Net Income	$ 59.0	$ 47.2	$ 216.7	$ 145.4
Basic and diluted net income per unit:
Common units	$ 0.26	$ 0.23	$ 0.99	$ 0.72
Class B units	$ (0.02)	$ 0.00	$ 0.21	$ 0.04
Cash distribution declared and paid to common units	$ 0.5325	$ 0.5250	$ 1.5950	$ 1.5675
Cash distribution declared and paid to class B units	$ 0.30	$ 0.30	$ 0.90	$ 0.90
Weighted-average number of units outstanding:
Common units	192.6	175.7	186.8	172.5
Class B units	22.9	22.9	22.9	22.9