LONG-TERM DEBT - Covenants and Guarantees (Details)	Dec. 31, 2017	Sep. 03, 2015
Guarantees
Ownership of subsidiaries (as a percent)	100.00%
Note and Guarantee Agreement
Financial covenants
Ratio under debt agreement for entity to make dividends (as a percent)	60.00%
Sinosure Credit Facility
Financial covenants
Dividend cap as a percentage of consolidated net income	50.00%
Korean Export Credit Facility | Term Loan
Financial covenants
Dividend cap as a percentage of consolidated net income	50.00%
Refinancing Facility
Financial covenants
Dividend cap as a percentage of consolidated net income	50.00%	50.00%