INCOME TAXES (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income tax expense on income from continuing operations
Federal									$ 38.9	$ 26.5	$ 38.1
State									3.2	1.8	5.4
Total									42.1	28.3	43.5
Deferred									(9.1)	(3.2)	3.2
Provision for income taxes	4.4	11.2	15.3	2.1	3.1	10.6	9.6	1.8	33.0	25.1	46.7
Difference of Income tax expense from amounts computed by applying the statutory federal rate to income from continuing operations
Computed federal income tax expense									29.7	24.9	41.2
State income taxes									0.5	1.4	5.0
Deferred tax adjustment									(1.4)
Separation costs									1.7
Unrecognized tax benefit									1.5
Other-net									1.0	(1.2)	0.5
Provision for income taxes	4.4	11.2	15.3	2.1	3.1	10.6	9.6	1.8	33.0	25.1	46.7
Deferred tax assets:
Benefit plans	54.0				52.5				54.0	52.5
Insurance reserves	9.7				7.8				9.7	7.8
Allowance for doubtful accounts	1.7				1.9				1.7	1.9
Reserves	1.7				2.5				1.7	2.5
Other	0.3				1.9				0.3	1.9
Total deferred tax assets	67.4				66.6				67.4	66.6
Deferred tax liabilities:
Basis differences for property and equipment	292.6				301.1				292.6	301.1
Capital Construction Fund	3.3				3.3				3.3	3.3
Joint ventures and other investments	3.8				6.0				3.8	6.0
Deferred revenue	10.9				8.0				10.9	8.0
Amortization	2.1				2.0				2.1	2.0
Total deferred tax liabilities	312.7				320.4				312.7	320.4
Net deferred tax liability	$ 245.3				$ 253.8				$ 245.3	$ 253.8