Allowance for Expected Credit Losses Balances of Premiums Receivable (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Balance, beginning of period	$ 189,671	$ 193,369
Balance, end of period	199,356	199,356
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	334	578
Current period change for expected credit losses	626	2,202
Writeoffs of uncollectable accounts receivable	(46)	(1,866)
Balance, end of period	$ 914	$ 914