LEASES - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Jan. 01, 2019
Operating Leases, Rent Expense	$ 40,100,000	$ 42,500,000
Right-of-use assets - operating leases			$ 133,832,000	$ 109,600,000
Weighted average remaining lease term under finance leases			2 years
Weighted average remaining lease term under operating leases			5 years
Weighted average discount rate under finance leases			5.20%
Weighted average discount rate under operating leases			5.60%
Operating Leases, Income Statement, Sublease Revenue	$ 6,500,000	$ 7,100,000
Lessor, Operating Lease, Renewal Term			5 years
Lessee, Operating Lease, Liability, Lease Not yet Commenced, Payments Due			$ 12,300,000
Lessee, Operating Lease, Liability, Payments, Due			$ 163,749,000
Minimum
Discount rate			1.50%	1.50%
Lessee, Finance Lease, Lease Not yet Commenced, Term of Contract			3 years
Maximum
Discount rate			6.90%	6.90%
Lessee, Finance Lease, Lease Not yet Commenced, Term of Contract			5 years
Accumulated Deficit | Accounting Standards Update 2016-02
Cumulative effect adjustment				$ 0
600 West Chicago [Member]
Lessee, Operating Lease, Liability, Payments, Due			$ 79,400,000