LEASES (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) office
Leases [Abstract]
Number of buildings and offices under operating leases | office		106
Operating right-of-use lease assets	$ 58,985	$ 58,985
Operating lease liabilities	$ 62,808	$ 62,808
Weighted-average remaining lease term: Operating leases	6 years 4 months 24 days	6 years 4 months 24 days
Weighted-average discount rate: Operating leases	3.83%	3.83%
Operating lease cost	$ 3,818	$ 11,650
Short-term lease costs	62	284
Variable lease cost	623	1,751
Less sublease income	(228)	(696)
Total lease cost	4,275	12,989
Operating cash flows paid for operating lease amounts	3,800	11,500
Right-of-use assets in exchange for operating lease liabilities	8,800	72,500
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remainder of 2019	3,778	3,778
2020	14,936	14,936
2021	13,596	13,596
2022	10,086	10,086
2023	7,193	7,193
Thereafter	21,498	21,498
Total minimum lease payments	71,087	71,087
Less: amount of lease payments representing interest	(8,279)	(8,279)
Operating lease liabilities	$ 62,808	62,808
Undiscounted lease payments under an operating lease that had not yet commenced		$ 0