Investments - Scheduled Maturities (Details) - USD ($) $ in Thousands |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Amortized Cost | ||
| Due in one year or less | $ 138,776 | $ 76,087 |
| Due after one through five years | 406,986 | 352,282 |
| Due after five through ten years | 380,737 | 318,728 |
| Due after ten years | 17,127 | 5,900 |
| Asset-backed securities | 170,153 | 171,990 |
| Total investments | 1,113,779 | 924,987 |
| Fair Value | ||
| Due in one year or less | 139,113 | 76,104 |
| Due after one through five years | 417,208 | 347,701 |
| Due after five through ten years | 394,180 | 310,633 |
| Due after ten years | 17,797 | 5,727 |
| Asset-backed securities | 172,642 | 171,325 |
| Total investments | $ 1,140,940 | $ 911,490 |