BUSINESS SEGMENT INFORMATION (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Operating revenues [Abstract]
External customers	$ 348.4	$ 352.5	$ 1,862.4	$ 1,971.0
Intersegment	0	0	0	0
Total operating revenues	348.4	352.5	1,862.4	1,971.0
Operating income (loss)	18.3	30.4	119.3	169.8
Natural weather hedge cost (benefit)	0.3	(0.1)	2.6	0.3
Merger related costs incurred and expensed	0.4		2.8
Gas Distribution [Member]
Operating revenues [Abstract]
External customers	235.4	229.0	1,485.7	1,571.3
Intersegment	4.5	4.5	28.9	30.5
Total operating revenues	239.9	233.5	1,514.6	1,601.8
Operating income (loss)	21.3	20.9	115.1	141.5
Shipping [Member]
Operating revenues [Abstract]
External customers	78.4	83.9	239.1	253.4
Intersegment	0	0	0	0
Total operating revenues	78.4	83.9	239.1	253.4
Operating income (loss)	(3.7)	3.6	(5.2)	7.3
Wholesale Marketing [Member]
Operating revenues [Abstract]
External customers	1.6	7.1	12.8	20.5
Intersegment	0.7	1.1	8.4	9.3
Total operating revenues	2.3	8.2	21.2	29.8
Operating income (loss)	(4.7)	0.7	(0.1)	8.1
Other [Member]
Operating revenues [Abstract]
External customers	33.0	32.5	124.8	125.8
Intersegment	0.5	0.5	1.3	1.6
Total operating revenues	33.5	33.0	126.1	127.4
Operating income (loss)	6.4	6.4	15.7	14.8
Corporate and eliminations [Member]
Operating revenues [Abstract]
External customers	0	0	0	0
Intersegment	(5.7)	(6.1)	(38.6)	(41.4)
Total operating revenues	(5.7)	(6.1)	(38.6)	(41.4)
Operating income (loss)	$ (1.0)	$ (1.2)	$ (6.2)	$ (1.9)