Investments - Schedule of Proceeds From Sales and Maturities of Marketable Securities Plus Resulting Realized Gains and Losses (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Investments Debt And Equity Securities [Abstract] | |||
| Proceeds from the sales and maturities of marketable securities | $ 224,602 | $ 444,456 | $ 464,494 |
| Realized gains | 997 | 4 | 9 |
| Realized losses | $ 497 | $ 268 | $ 3 |