Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Fair Value of Debt) (Details)

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FAIR VALUE MEASUREMENTS (Fair Value of Debt) (Details) - Level 2 [Member] - USD ($)
$ in Millions
Mar. 31, 2016
Dec. 31, 2015
7% Senior Notes due 2020 [Member]    
Debt Fair Value [Line Items]    
Interest rate, stated percentage 7.00% 7.00%
Estimated fair values of senior notes $ 447.3 $ 443.1
5.375% Senior Notes due 2022 [Member]    
Debt Fair Value [Line Items]    
Interest rate, stated percentage 5.375% 5.375%
Estimated fair values of senior notes $ 257.7 $ 249.4
2.5% Convertible Senior Notes Due 2019 [Member]    
Debt Fair Value [Line Items]    
Interest rate, stated percentage 2.50% 2.50%
Estimated fair values of convertible senior notes $ 270.2 $ 280.2
Fixed Rate Debt With Noncontrolling Interest Partner [Member]    
Estimate of fair value not practicable [Abstract]    
Face amount of debt $ 26.3 $ 26.9