Related Party Transactions - Schedule of AmTrust Quota Share Arrangement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Total	$ 24,305	$ 94,898	$ 76,828	$ 411,986
Net loss and LAE	(9,065)	(140,860)	(41,159)	(415,110)
Commission and other acquisition expenses	(9,651)	(32,763)	(29,778)	(152,036)
Quota Share Reinsurance Agreements | AmTrust Financial Services, Inc.
Related Party Transaction [Line Items]
Gross and net premiums written	(5,635)	21,405	(10,340)	(564,199)
Total	12,981	74,407	41,205	344,370
Net loss and LAE	(2,441)	(126,945)	(21,456)	(373,980)
Commission and other acquisition expenses	$ (5,447)	$ (25,758)	$ (16,221)	$ (127,623)