Allowance for Expected Credit Losses - Balances of Premiums Receivable (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Balance, beginning of period	$ 170,953	$ 179,147
Balance, end of period	167,096	170,915
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	1,808	1,754
Current period change for expected credit losses	401	1,768
Writeoffs of uncollectable accounts receivable	(476)	(1,338)
Balance, end of period	$ 1,733	$ 2,184