Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Statement of Financial Position [Abstract]
Available for sale securities, amortized cost	$ 3,798,274	$ 3,803,835
Allowance for expected credit losses	4,031	3,399
Trading securities, cost	12,304	52,493
Equity investments at fair value, cost	120,665	145,411
Other investments, portion carried at fair value	2,137	2,077
Premium receivable, allowance for credit loss	$ 7,957	$ 8,141
Common shares, par value (in usd per share)	$ 0.01	$ 0.01
Common shares, shares authorized (in shares)	100,000,000	100,000,000
Common shares, shares issued (in shares)	64,020,611	63,763,789
Deferred tax expense (benefit) on accumulated other comprehensive income (loss)	$ (24,560)	$ (46,681)
Treasury shares (in shares)	12,606,968	12,606,968