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) - USD ($)
$ in Millions
Jun. 30, 2017
Dec. 31, 2016
Fixed Rate Debt With Noncontrolling Interest Partner [Member]    
Estimate of fair value not practicable [Abstract]    
Face amount of debt $ 38.7 $ 35.7
Level 2 [Member] | 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 $ 259.8 $ 259.7
Level 2 [Member] | 4.875% Senior Notes Due 2024 [Member]    
Debt Fair Value [Line Items]    
Interest rate, stated percentage 4.875% 4.875%
Estimated fair values of senior notes $ 583.8 $ 578.5
Level 2 [Member] | 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 $ 314.9 $ 294.6