LEASES (Lease Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 9,673	$ 8,515	$ 25,604	$ 24,478
Cost of revenues
Lessee, Lease, Description [Line Items]
Total operating lease costs	2,717	2,992	7,446	8,732
Software development
Lessee, Lease, Description [Line Items]
Total operating lease costs	1,910	1,628	4,913	4,412
Selling and marketing (excluding customer base amortization)
Lessee, Lease, Description [Line Items]
Total operating lease costs	3,452	2,636	8,876	7,725
General and administrative
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 1,594	$ 1,259	$ 4,369	$ 3,609