General - Allowance for Credit Losses on Premium Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Premiums Receivable, Allowance for Doubtful Accounts [Roll Forward]
Beginning balance	$ 10,000	$ 1,199	$ 1,445	$ 1,458
Provision during the period for expected credit losses	559	1,506	9,448	4,421
Write-off amounts during the period	(735)	(1,660)	(3,279)	(5,231)
Recoveries during the period of amounts previously written off	176	268	531	665
Ending balance	10,000	1,313	10,000	1,313
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	$ 1,199	$ 3,300	$ 1,458