Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Available for sale securities, amortized cost	$ 3,666,295	$ 2,361,575
Allowance for expected credit losses	0	552
Trading securities, cost	46,167	47,907
Equity investments at fair value, cost	229,055	113,709
Other investments, portion carried at fair value	$ 106,895	$ 44,116
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)	63,306,684	63,217,708
Deferred tax expense (benefit) on accumulated other comprehensive income (loss)	$ 14,278	$ 19,386
Treasury shares, number of shares (in shares)	9,325,180	9,325,180