LEASE COMMITMENTS - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Leases
Operating lease right-of-use assets	$ 82,099	$ 83,222
Operating lease liability, current	$ 15,935
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Operating lease liabilities	$ 64,592	$ 61,331
Total operating lease liabilities	80,527
Finance Leases
Finance leases included in property, plant and equipment, gross	31,735
Accumulated depreciation of finance leases included in property, plant and equipment, net	(1,095)
Total finance leases	$ 30,640
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, Plant and Equipment, Net
Current portion of finance lease liabilities	$ 3,389
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Long-term Debt and Capital Lease Obligations, Current
Noncurrent portion of finance lease liabilities	$ 20,412
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term Debt and Capital Lease Obligations
Total finance lease liabilities	$ 23,801		$ 8,353
Weighted Average Remaining Lease Term (in years)
Operating leases	6 years 4 months 24 days
Finance leases	7 years 3 months 18 days
Weighted Average Discount Rate
Operating leases	4.92%
Finance leases	5.66%