LEASES (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) office	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Leases [Abstract]
Number of buildings and offices under operating leases | office	105
Operating right-of-use lease assets	$ 59,620		$ 61,766
Operating lease liabilities	$ 63,757		$ 65,818
Weighted-average remaining lease term: Operating leases	6 years		6 years 2 months 12 days
Weighted-average discount rate: Operating leases	3.60%		3.70%
Operating lease cost	$ 4,164	$ 3,975
Short-term lease costs	21	121
Variable lease cost	811	561
Less sublease income	(254)	(237)
Total lease cost	4,742	4,420
Operating cash flows paid for operating lease amounts	4,100	3,900
Right-of-use assets in exchange for operating lease liabilities	1,600	$ 61,000
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remainder of 2020	12,180
2020	15,370
2021	11,764
2022	8,675
2023	6,756
Thereafter	16,489
Total minimum lease payments	71,234
Less: amount of lease payments representing interest	(7,477)
Operating lease liabilities	63,757		$ 65,818
Undiscounted lease payments under an operating lease that had not yet commenced	$ 0