SEGMENT REPORTING, ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property and equipment, net	$ 84,518	$ 83,303
Goodwill	1,617,853	1,611,535	$ 1,283,457
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	3,620,598	3,312,957
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	416,527	291,015
North America [Member]
Segment Reporting Information [Line Items]
Property and equipment, net	80,575	79,493
Goodwill	1,579,537	1,573,088	1,253,494
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	3,536,859	3,253,035
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	382,962	272,776
International [Member]
Segment Reporting Information [Line Items]
Property and equipment, net	3,943	3,810
Goodwill	38,316	38,447	$ 29,963
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	83,739	59,922
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	$ 33,565	$ 18,239