RETIREMENT AND DEFERRED COMPENSATION PLANS - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
United States
Components of net periodic benefit cost:
Service cost	$ 3,941	$ 3,562	$ 8,168	$ 7,139
Interest cost	1,604	1,536	3,215	3,523
Expected return on plan assets	(3,064)	(2,702)	(6,137)	(6,124)
Amortization of net loss	2,501	1,294	5,004	2,842
Amortization of prior service cost	0	0	0	0
Net periodic benefit cost	4,982	3,690	10,250	7,380
Foreign Plans
Components of net periodic benefit cost:
Service cost	2,071	1,767	4,149	3,535
Interest cost	208	340	426	680
Expected return on plan assets	(721)	(631)	(1,444)	(1,265)
Amortization of net loss	591	514	1,180	1,028
Amortization of prior service cost	44	95	89	192
Net periodic benefit cost	$ 2,193	$ 2,085	$ 4,400	$ 4,170