Net realized and unrealized gains - Proceeds from the Sale of Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of debt securities	$ 10,255	$ 19,123	$ 25,134	$ 47,405
Proceeds from sales of equity securities	3,887	62	28,496	549
Total proceeds from sales of investments in securities	$ 14,142	$ 19,185	$ 53,630	$ 47,954