SEGMENT REPORTING, ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Property and equipment, net	$ 84,648	$ 84,496
Goodwill	1,549,517	1,283,457	$ 1,254,866
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	3,122,574	2,873,441
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	271,956	222,191
North America [Member]
Segment Reporting Information [Line Items]
Goodwill	1,520,214	1,253,494	1,227,777
International [Member]
Segment Reporting Information [Line Items]
Goodwill	29,303	29,963	$ 27,089
Operating Segments [Member]
Segment Reporting Information [Line Items]
Property and equipment, net	84,648	84,496
Goodwill	1,549,517	1,283,457
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	3,122,574	2,873,441
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	271,956	222,191
Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Property and equipment, net	80,359	79,736
Goodwill	1,520,213	1,253,494
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	3,069,612	2,816,156
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	253,891	201,831
Operating Segments [Member] | International [Member]
Segment Reporting Information [Line Items]
Property and equipment, net	4,289	4,760
Goodwill	29,304	29,963
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	52,962	57,285
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	$ 18,065	$ 20,360