INCOME TAXES (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
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)	4.80%	4.40%	5.30%
Benefits and compensation (as a percent)	(0.90%)	(3.60%)	0.40%
Federal tax credits (as a percent)	0.00%	(3.50%)	(3.20%)
Other differences, net (as a percent)	(1.60%)	(0.60%)	(0.70%)
Effective income tax rate (as a percent)	37.30%	31.70%	36.80%
Reconciliation of federal income taxes to the provision for income taxes reported in the income statement
Statutory federal income tax	$ 76.9	$ 69.1	$ 69.7
State income taxes, net	10.5	8.7	10.6
Benefits and compensation	(1.9)	(7.2)	0.8
Federal tax credits	0	(7.0)	(6.4)
Other differences, net	(3.6)	(1.0)	(1.5)
Effective income tax	81.9	62.6	73.2
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at the beginning of the period	0.3	0.5	4.8
Increase related to tax positions taken in prior years	0.7	0	0.4
Decrease related to tax positions taken in prior years	(0.4)	0	(0.5)
Decrease related to settlements	(0.6)	0	(4.2)
Decrease related to lapse of statutes	0	(0.2)	0
Balance at the end of the period	0	0.3	0.5
Unrecognized tax benefits, additional disclosures
Accrued interest related to unrecognized tax benefits	0	0.1
Accrued penalties related to unrecognized tax benefits	$ 0	$ 0