INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	16.90%	17.50%	19.20%	18.40%
Unrecognized tax benefits with certainty of deductibility but with uncertainty about the timing of deductions	$ 0		$ 0		$ 0	$ 700
Unrecognized tax benefits	$ 1,800		1,800		7,100	11,400
Accrued interest related to unrecognized tax benefits			$ 600		$ 40	$ 2,400