Allowance for Expected Credit Losses - Premiums receivable (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Credit Loss [Abstract]
Balance at beginning of period		$ 2,633,280	$ 2,064,586
Balance at end of period		3,624,777	2,633,280
Allowance for Expected Credit Losses
Balance at beginning of period		39,958	37,781
Change for provision of expected credit losses	[1]	(4,556)	2,177
Balance at end of period		35,402	39,958
Write-offs charged against the allowance		$ 11,400	$ 3,800

[1] Amounts deemed uncollectible are written-off in operating expenses. For the 2022 and 2021 periods, amounts written off totaled $11.4 million and $3.8 million, respectively.