FAIR VALUE MEASUREMENTS - Summary of fair value Level 2 debt (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Term loan	$ 427,070	$ 429,143
Revolving credit facility	14,000	0
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Term loan	330,979	428,071
Revolving credit facility	$ 10,850	$ 0