LEASES - Lease Data (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2018
Lease Costs
Operating lease expense	$ 85,521	$ 86,451
Short-term lease expense	8,307	15,130
Total lease expense	93,828	101,581
Other Lease Information
Operating cash flows from operating leases	85,244	74,177
Right-of-use lease assets obtained in exchange for new lease liabilities	$ 52,931	$ 95,005
Lease Term and Discount Rate
Weighted average remaining lease term (in years)	6 years 4 months 24 days	6 years 9 months 18 days
Weighted average discount rate (percent)	3.00%	3.20%
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term, excluding Chicago office space (in years)	4 years 6 months
Chicago office space
Lessee, Lease, Description [Line Items]
Lease term (in years)			15 years