General - Allowance for Credit Losses on Premium Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Premiums Receivable, Allowance for Doubtful Accounts [Roll Forward]
Beginning balance	$ 10,000	$ 1,321	$ 1,445	$ 1,458
Provision during the period for expected credit losses	719	331	8,888	1,894
Write-off amounts during the period	(885)	(680)	(2,543)	(2,550)
Recoveries during the period of amounts previously written off	166	227	355	397
Ending balance	10,000	1,199	10,000	1,199
Cumulative Effect, Period Of Adoption, Adjustment [Member]
Premiums Receivable, Allowance for Doubtful Accounts [Roll Forward]
Beginning balance	0	0	1,855	0
Cumulative Effect, Period Of Adoption, Adjusted Balance [Member]
Premiums Receivable, Allowance for Doubtful Accounts [Roll Forward]
Beginning balance	$ 10,000	$ 1,321	$ 3,300	$ 1,458