INCOME TAXES (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current:
Federal									$ (24.3)	$ 38.9	$ 26.5
State									(1.0)	3.2	1.8
Total									(25.3)	42.1	28.3
Deferred									57.5	(9.1)	(3.2)
Provision for income taxes	7.1	6.4	12.8	5.9	4.4	11.2	15.3	2.1	32.2	33.0	25.1
Difference of Income tax expense from amounts computed by applying the statutory federal rate to income from continuing operations before income taxes
Computed federal income tax expense (as a percent)									35.00%	35.00%	35.00%
Discontinued operations (as a percent)									0.00%	(0.20%)	(0.10%)
State income tax (as a percent)									2.90%	0.60%	2.10%
Deferred tax adjustment (as a percent)									0.00%	(1.60%)	0.00%
Separation costs (as a percent)									0.00%	2.00%	0.00%
Unrecognized tax benefit (as a percent)									(2.10%)	1.70%	0.00%
Other-net (as a percent)									1.70%	1.30%	(1.60%)
Provision for income taxes (as a percent)									37.50%	38.80%	35.40%
Deferred tax assets:
Benefit plans	41.8				54.0				41.8	54.0
Insurance reserves	10.0				9.7				10.0	9.7
Allowance for doubtful accounts	1.3				1.7				1.3	1.7
Reserves	6.0				1.7				6.0	1.7
Foreign losses and unremitted earnings	3.1								3.1
Alternative minimum tax credits	1.4								1.4
Other	(0.2)				0.3				(0.2)	0.3
Total deferred tax assets	63.4				67.4				63.4	67.4
Deferred tax liabilities:
Basis differences for property and equipment	278.0				292.6				278.0	292.6
Capital Construction Fund	83.4				3.3				83.4	3.3
Joint ventures and other investments	4.6				3.8				4.6	3.8
Deferred revenue	11.4				10.9				11.4	10.9
Amortization	3.0				2.1				3.0	2.1
Total deferred tax liabilities	380.4				312.7				380.4	312.7
Net deferred tax liability	$ 317.0				$ 245.3				$ 317.0	$ 245.3