Quarterly report pursuant to Section 13 or 15(d)

UNEARNED REVENUE (Details)

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UNEARNED REVENUE (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Change in Contract with Customer, Liability [Roll Forward]      
Balance, beginning of period $ 127,075 $ 117,614 $ 117,614
Deferral of unearned revenue 47,737 47,725 166,053
Recognition of unearned revenue (39,958) (38,809) (156,592)
Balance, end of period $ 134,854 $ 126,530 $ 127,075