FAIR VALUE MEASUREMENTS - Summary of valuation of financial instruments measured at fair value on recurring basis (Details) - USD ($)
$ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
| Available-for-sale securities |
|
|
| Available-for-sale securities |
$ 11,512
|
$ 13,031
|
| Fair Value, Measurements, Recurring | Fair value measurement |
|
|
| Assets: |
|
|
| Investments measured at Net Asset Value - Trading securities |
5,944
|
6,031
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
11,512
|
13,031
|
| Fair Value, Measurements, Recurring | Fair value measurement | Municipal Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
9,764
|
13,031
|
| Fair Value, Measurements, Recurring | Fair value measurement | Corporate Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
1,748
|
0
|
| Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets, Level 1 | Fair value measurement |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
0
|
0
|
| Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets, Level 1 | Fair value measurement | Municipal Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
0
|
0
|
| Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets, Level 1 | Fair value measurement | Corporate Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
0
|
0
|
| Fair Value, Measurements, Recurring | Significant other observable inputs, Level 2 | Fair value measurement |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
11,512
|
13,031
|
| Fair Value, Measurements, Recurring | Significant other observable inputs, Level 2 | Fair value measurement | Municipal Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
9,764
|
13,031
|
| Fair Value, Measurements, Recurring | Significant other observable inputs, Level 2 | Fair value measurement | Corporate Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
1,748
|
0
|
| Fair Value, Measurements, Recurring | Significant unobservable inputs, Level 3 | Fair value measurement |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
0
|
0
|
| Fair Value, Measurements, Recurring | Significant unobservable inputs, Level 3 | Fair value measurement | Municipal Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
0
|
0
|
| Fair Value, Measurements, Recurring | Significant unobservable inputs, Level 3 | Fair value measurement | Corporate Obligations |
|
|
| Available-for-sale securities |
|
|
| Available-for-sale securities |
$ 0
|
$ 0
|