FAIR VALUE MEASUREMENTS - Financial instruments measured at fair value on recurring basis (Details) - USD ($)
$ in Thousands |
Mar. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
$ 49,662
|
$ 51,403
|
$ 61,429
|
| State and municipal |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
11,535
|
20,255
|
21,454
|
| Asset-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
6,048
|
6,371
|
7,517
|
| Mortgage-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
32,079
|
24,777
|
32,458
|
| Quoted Prices in Active Markets for Identical Assets Level 1 |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Significant Other Observable Inputs Level 2 |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
49,662
|
51,403
|
61,429
|
| Significant Unobservable Inputs Level 3 |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
49,662
|
51,403
|
61,429
|
| Recurring basis | State and municipal |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
11,535
|
20,255
|
21,454
|
| Recurring basis | Asset-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
6,048
|
6,371
|
7,517
|
| Recurring basis | Mortgage-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
32,079
|
24,777
|
32,458
|
| Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | State and municipal |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Asset-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis | Quoted Prices in Active Markets for Identical Assets Level 1 | Mortgage-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis | Significant Other Observable Inputs Level 2 |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
49,662
|
51,403
|
61,429
|
| Recurring basis | Significant Other Observable Inputs Level 2 | State and municipal |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
11,535
|
20,255
|
21,454
|
| Recurring basis | Significant Other Observable Inputs Level 2 | Asset-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
6,048
|
6,371
|
7,517
|
| Recurring basis | Significant Other Observable Inputs Level 2 | Mortgage-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
32,079
|
24,777
|
32,458
|
| Recurring basis | Significant Unobservable Inputs Level 3 |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis | Significant Unobservable Inputs Level 3 | State and municipal |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis | Significant Unobservable Inputs Level 3 | Asset-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
0
|
0
|
0
|
| Recurring basis | Significant Unobservable Inputs Level 3 | Mortgage-backed securities |
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
| Investments in available-for-sale securities (at fair value) |
$ 0
|
$ 0
|
$ 0
|