Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Fixed maturity investments trading, amortized cost	$ 16,754,568	$ 15,038,551
Short-term investments, amortized cost	$ 6,521,007	$ 4,671,581
Preference shares, par value (in dollars per share)	$ 1.00	$ 1.00
Preference shares, shares issued (in shares)	30,000	30,000
Preference shares, shares outstanding (in shares)	30,000	30,000
Common shares, par value (in dollars per share)	$ 1.00	$ 1.00
Common shares, shares issued (in shares)	51,173,930	43,717,836
Common shares, shares outstanding (in shares)	51,173,930	43,717,836