SEGMENT INFORMATION - Reconciliation of Segment Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item
Segment assets	$ 497,327	$ 264,450
Property and equipment, net	70,859	53,292
Goodwill	894,709	770,226	$ 170,990
Indefinite-lived intangible assets	171,486	153,447
Definite-lived intangible assets, net	132,809	175,124
Assets before deferred tax assets	1,767,190	1,416,539
Add: Deferred tax assets	40,837	50,723
TOTAL ASSETS	1,808,027	1,467,262
North America
Segment Reporting, Asset Reconciling Item
Segment assets	485,448	253,582
Property and equipment, net	65,670	49,487
Goodwill	824,037	696,291	140,930
Indefinite-lived intangible assets	158,678	140,034
Definite-lived intangible assets, net	131,117	169,054
Assets before deferred tax assets	1,664,950	1,308,448
Europe
Segment Reporting, Asset Reconciling Item
Segment assets	11,879	10,868
Property and equipment, net	5,189	3,805
Goodwill	70,672	73,935	$ 30,060
Indefinite-lived intangible assets	12,808	13,413
Definite-lived intangible assets, net	1,692	6,070
Assets before deferred tax assets	$ 102,240	$ 108,091