SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adoption of ASU 2016-02 (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 69,845	$ 72,377	$ 83,222	$ 0
Prepaid and other	122,613	115,048	116,862	118,245
Property, plant and equipment	1,198,748	1,087,678	997,489	991,613
Current maturities of long-term obligations, net of unamortized debt issuance costs	65,666	65,988	65,309	62,678
Accounts payable, accrued and other liabilities	662,463	573,028	545,707	525,199
Operating lease liabilities	52,212	55,276	61,331	0
Long-Term Obligations, net of unamortized debt issuance costs	$ 1,054,998	$ 1,085,453	1,129,238	$ 1,125,993
Accounting Standards Update 2016-02 | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets			83,222
Prepaid and other			(1,383)
Property, plant and equipment			5,876
Current maturities of long-term obligations, net of unamortized debt issuance costs			2,631
Accounts payable, accrued and other liabilities			20,508
Operating lease liabilities			61,331
Long-Term Obligations, net of unamortized debt issuance costs			$ 3,245