DEBT - (Long-term debt) (Table) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Total long-term debt	$ 1,985.4	$ 2,085.5
Revolving credit facility [Member]
Debt Instrument [Line Items]
Total long-term debt	460.0	560.0
Senior notes due 2013 [Member]
Debt Instrument [Line Items]
Total long-term debt	350.4	350.5
Senior notes due 2015 [Member]
Debt Instrument [Line Items]
Total long-term debt	250.0	250.0
Senior notes due 2016 [Member]
Debt Instrument [Line Items]
Total long-term debt	325.0	325.0
Senior notes due 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 600.0	$ 600.0