ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Contract assets and liabilities (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Mar. 31, 2020 |
Mar. 31, 2019 |
Dec. 31, 2019 |
|
| Contract assets: | |||
| Unbilled receivables | $ 5,799 | $ 6,529 | $ 3,763 |
| Contract liabilities: | |||
| Customer advances and unearned income | 2,667 | 3,836 | 3,048 |
| Unearned event income | $ 11,194 | $ 8,201 | $ 6,645 |