Investments and fair value measurements - Summary of Accrued Interest (Details) - USD ($) $ in Thousands |
Mar. 31, 2022 |
Dec. 31, 2021 |
|---|---|---|
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Accrued interest receivable on investments | $ 437 | $ 899 |
| Debt Securities | ||
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Accrued interest receivable on investments | 429 | 886 |
| Corporate debt securities | ||
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Accrued interest receivable on investments | 409 | 874 |
| U.S. Treasury securities | ||
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Accrued interest receivable on investments | 20 | 12 |
| Mortgage loans | ||
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Accrued interest receivable on investments | $ 8 | $ 13 |