Quarterly report pursuant to Section 13 or 15(d)

STOCK-BASED COMPENSATION (Narrative) (Details)

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STOCK-BASED COMPENSATION (Narrative) (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Share-based Compensation [Abstract]        
Stock-based compensation cost $ 3.6 $ 2.8 $ 9.7 $ 8.0
Capitalized stock-based compensation cost 1.4 $ 1.1 3.9 $ 3.2
Unrecognized compensation expense $ 15.5   $ 15.5  
Weighted average period of expense recognition period     1 year 7 months 17 days