OTHER ASSETS - Schedule of Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Equity method investments	$ 72,371	$ 123,923
Other equity investments	44,625	45,222
Post-retirement plan assets	28,081	22,659
Other	39,754	49,841
Total other assets	$ 184,831	$ 241,645