Marketable Investment Securities - Schedule of Unrealized Gains (Losses) on Available-for-Sale Securities (Details) - USD ($) $ in Thousands |
Jun. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Debt Securities, Available-for-sale [Line Items] | ||
| Debt securities | $ 471,125 | $ 904,022 |
| Corporate bonds | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Amortized Cost | 381,071 | 567,926 |
| Unrealized Gains | 132 | 518 |
| Unrealized Losses | (2) | (2) |
| Debt securities | 381,201 | 568,442 |
| Other debt securities | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Amortized Cost | 89,923 | 335,572 |
| Unrealized Gains | 1 | 8 |
| Unrealized Losses | 0 | 0 |
| Debt securities | 89,924 | 335,580 |
| Total available-for-sale debt securities | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Amortized Cost | 470,994 | 903,498 |
| Unrealized Gains | 133 | 526 |
| Unrealized Losses | (2) | (2) |
| Debt securities | $ 471,125 | $ 904,022 |