ACQUISITIONS (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
KA Steel [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue	$ 2,462.6	$ 2,351.5	$ 1,854.6
Business Acquisition, Pro Forma Net Income (Loss)	160.1	240.0	62.6
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 2.00	$ 3.00	$ 0.79
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 1.98	$ 2.97	$ 0.78
SunBelt [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue		1,987.4	1,743.2
Business Acquisition, Pro Forma Net Income (Loss)		$ 140.6	$ 80.4
Business Acquisition, Pro Forma Earnings Per Share, Basic		$ 1.76	$ 1.02
Business Acquisition, Pro Forma Earnings Per Share, Diluted		$ 1.74	$ 1.01