Allowance for Expected Credit Losses - Reinsurance recoverables (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Credit Loss [Abstract]
Balance at beginning of period	$ 5,938,511	$ 4,314,515	$ 5,880,735	$ 4,500,802
Balance at end of period	6,356,456	5,358,852	6,356,456	5,358,852
Allowance for Expected Credit Losses
Balance at beginning of period	14,740	11,029	13,230	11,636
Change for provision of expected credit losses	2,626	1,802	4,136	1,195
Balance at end of period	$ 17,366	$ 12,831	$ 17,366	$ 12,831