LEASES - Narrative (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lessee, Lease, Description [Line Items]
Cumulative gain recognized from sale leaseback transaction		$ 644,738	$ 881,443	$ 1,334,260	$ 1,764,360
Retained Earnings (Accumulated Deficit)
Lessee, Lease, Description [Line Items]
Cumulative gain recognized from sale leaseback transaction		$ (1,017,037)	$ (775,578)	(360,664)	$ 25,791
Application of amended leasing guidance
Lessee, Lease, Description [Line Items]
Cumulative gain recognized from sale leaseback transaction				4,719
Tax on gain of sales lease buyback transaction	$ 1,700
Application of amended leasing guidance | Retained Earnings (Accumulated Deficit)
Lessee, Lease, Description [Line Items]
Cumulative gain recognized from sale leaseback transaction				$ 4,719
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease terms		1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease terms		30 years
Renewal term		15 years