| VARIABLE INTEREST ENTITIES - Narrative (Details) - Aeroleo - USD ($) $ in Millions | Sep. 30, 2019 | Dec. 31, 2018 | Dec. 31, 2011 | 
|---|---|---|---|
| Variable Interest Entity [Line Items] | |||
| Economic interest percent | 50.00% | 50.00% | |
| Voting interest percent | 20.00% | 20.00% | |
| Variable Interest Entity, Primary Beneficiary | |||
| Variable Interest Entity [Line Items] | |||
| Assets | $ 14.2 | $ 11.9 | |
| Liabilities | $ 5.9 | $ 4.5 | 
| X | ||||||||||
| 
- Definition Equity Method Investment, Voting Ownership Percentage No definition available. 
 | 
| X | ||||||||||
| 
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
 | 
| X | ||||||||||
| 
- Definition The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
 | 
| X | ||||||||||
| 
- Definition The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
 | 
| X | ||||||||||
| 
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
 | 
| X | ||||||||||
| 
- Details 
 | 
| X | ||||||||||
| 
- Details 
 |