BUSINESS SEGMENT INFORMATION (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Operating revenues [Abstract]
External customers	$ 477.0	$ 425.6	$ 1,514.0	$ 1,618.5
Intersegment	0	0	0	0
Total operating revenues	477.0	425.6	1,514.0	1,618.5
Operating income (loss)	35.2	43.4	101.0	139.4
Natural weather hedge benefit (cost)	(0.6)	0.9	(2.3)	(0.4)
Merger related costs incurred and expensed	0.9		2.4
Gas Distribution [Member]
Operating revenues [Abstract]
External customers	350.5	292.3	1,250.3	1,342.3
Intersegment	8.4	7.2	24.4	26.0
Total operating revenues	358.9	299.5	1,274.7	1,368.3
Operating income (loss)	27.9	27.4	93.8	120.6
Shipping [Member]
Operating revenues [Abstract]
External customers	79.9	86.0	160.7	169.5
Intersegment	0	0	0	0
Total operating revenues	79.9	86.0	160.7	169.5
Operating income (loss)	(0.3)	4.2	(1.5)	3.7
Wholesale Marketing [Member]
Operating revenues [Abstract]
External customers	7.1	7.8	11.2	13.4
Intersegment	1.5	2.5	7.7	8.2
Total operating revenues	8.6	10.3	18.9	21.6
Operating income (loss)	1.5	2.7	4.6	7.4
Other [Member]
Operating revenues [Abstract]
External customers	39.5	39.5	91.8	93.3
Intersegment	0.4	0.5	0.8	1.1
Total operating revenues	39.9	40.0	92.6	94.4
Operating income (loss)	7.9	8.7	9.3	8.4
Corporate and eliminations [Member]
Operating revenues [Abstract]
External customers	0	0	0	0
Intersegment	(10.3)	(10.2)	(32.9)	(35.3)
Total operating revenues	(10.3)	(10.2)	(32.9)	(35.3)
Operating income (loss)	$ (1.8)	$ 0.4	$ (5.2)	$ (0.7)