INCOME TAXES RECONCILIATION (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of federal income taxes to the provision for income taxes reported in the income statement (as a percent)
Statutory federal income tax rate (as a percent)	35.00%	35.00%	35.00%
State income tax rate, net (as a percent)	7.50%	3.70%	4.90%
Benefits and compensation (as a percent)	(0.90%)	(1.00%)	(2.60%)
Other differences, net (as a percent)	(0.60%)	(0.60%)	(4.30%)
Effective income tax rate (as a percent)	41.00%	37.10%	33.00%
Reconciliation of federal income taxes to the provision for income taxes reported in the income statement
Statutory federal income tax	$ 165.0	$ 148.9	$ 124.9
State income taxes, net	35.5	15.9	17.6
Benefits and compensation	(4.3)	(4.1)	(9.3)
Other differences, net	(2.8)	(2.7)	(15.3)
Provision for income taxes	193.4	158.0	117.9
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at the beginning of the period	3.6	11.3	22.4
Increase related to tax positions taken in prior years	0	2.2	0.9
Decrease related to tax positions taken in prior years	(0.1)	(8.7)	(6.7)
Increase related to tax positions taken in current year	0.5	0.3	0.6
Decrease related to settlements	0	(1.5)	(5.7)
Decrease related to lapse of statutes	(0.7)	0	(0.2)
Balance at the end of the period	3.3	3.6	11.3
Unrecognized tax benefits, additional disclosures
Accrued interest related to unrecognized tax benefits	0.3	0.8
Accrued penalties related to unrecognized tax benefits	0.2	0.4
Unrecognized tax benefits related to continuing operations that could affect our effective tax rate, if recognized	2.2
Reasonable possibility of decrease in unrecognized tax benefits with the next 12 months due to settlement of open examinations	$ (1.3)