INCOME TAXES RECONCILIATION (Details) (USD $)	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)	4.80%	4.80%	4.40%
Benefits and compensation (as a percent)	(1.00%)	(0.90%)	(3.60%)
Federal tax credits (as a percent)	0.00%	0.00%	(3.50%)
Other differences, net (as a percent)	(1.20%)	(1.60%)	(0.60%)
Effective income tax rate (as a percent)	37.60%	37.30%	31.70%
Reconciliation of federal income taxes to the provision for income taxes reported in the income statement
Statutory federal income tax	$ 78,900,000	$ 76,900,000	$ 69,100,000
State income taxes, net	10,900,000	10,500,000	8,700,000
Benefits and compensation	(2,200,000)	(1,900,000)	(7,200,000)
Federal tax credits	0	0	(7,000,000)
Other differences, net	(2,900,000)	(3,600,000)	(1,000,000)
Effective income tax	84,700,000	81,900,000	62,600,000
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at the beginning of the period	0	300,000	500,000
Increase related to tax positions taken in prior years	0	700,000	0
Decrease related to tax positions taken in prior years	0	(400,000)	0
Decrease related to settlements	0	(600,000)	0
Decrease related to lapse of statutes	0	0	(200,000)
Balance at the end of the period	0	0	300,000
Unrecognized tax benefits, additional disclosures
Accrued interest related to unrecognized tax benefits	0	0
Accrued penalties related to unrecognized tax benefits	$ 0	$ 0.0