Segment Information - Underwriting Results and Reconciliation from Reportable Segments and Other's Category Net Income (Loss) to Consolidated (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Segment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reporting segments | Segment			2
Net Income (Loss) [Abstract]
Gross premiums written	$ 3,517	$ 35,844	$ 20,233	$ (523,178)
Net premiums written	3,031	35,944	17,493	(525,995)
Total	24,305	94,898	76,828	411,986
Other insurance revenue	261	554	919	2,120
Net loss and loss adjustment expenses ("loss and LAE")	(9,065)	(140,860)	(41,159)	(415,110)
Commission and other acquisition expenses	(9,651)	(32,763)	(29,778)	(152,036)
General and administrative expenses	(2,448)	(2,084)	(7,118)	(9,035)
Underwriting (loss) income	3,402	(80,255)	(308)	(162,075)
Reconciliation to net income (loss) from continuing operations
Net investment income and realized gains on investment	16,819	25,923	69,005	102,052
Total other-than-temporary impairment losses	(962)	(165)	(2,468)	(165)
Interest and amortization expenses	(4,832)	(4,831)	(14,493)	(14,490)
Foreign exchange and other losses, net	(6,536)	7,827	(634)	14,013
Other general and administrative expenses	(5,712)	(6,814)	(18,853)	(28,640)
Income tax benefit (expense)	(17)	(87)	(14)	977
Income (loss) from continuing operations	$ 2,162	$ (58,402)	$ 32,235	$ (88,328)
Net loss and LAE ratio	36.90%	147.60%	52.90%	100.20%
Commission and other acquisition expense ratio	39.30%	34.30%	38.30%	36.70%
General and administrative expense ratio	33.20%	9.30%	33.40%	9.10%
Expense ratio	72.50%	43.60%	71.70%	45.80%
Combined ratio	109.40%	191.20%	124.60%	146.00%
Assets [Abstract]
Assets	$ 3,054,704		$ 3,054,704		$ 3,568,196
Operating Segments
Assets [Abstract]
Assets	2,570,192		2,570,192		3,011,647
Operating Segments | Diversified Reinsurance
Net Income (Loss) [Abstract]
Gross premiums written	9,152	$ 14,439	30,573	$ 41,021
Net premiums written	8,666	14,539	27,591	38,204
Total	11,323	20,492	35,381	68,256
Other insurance revenue	261	554	919	2,120
Net loss and loss adjustment expenses ("loss and LAE")	(6,624)	(13,807)	(19,703)	(40,695)
Commission and other acquisition expenses	(4,204)	(7,005)	(13,557)	(24,413)
General and administrative expenses	(1,818)	(1,849)	(5,177)	(6,972)
Underwriting (loss) income	$ (1,062)	$ (1,615)	$ (2,137)	$ (1,704)
Reconciliation to net income (loss) from continuing operations
Net loss and LAE ratio	57.20%	65.60%	54.30%	57.80%
Commission and other acquisition expense ratio	36.30%	33.30%	37.30%	34.70%
General and administrative expense ratio	15.70%	8.80%	14.30%	9.90%
Expense ratio	52.00%	42.10%	51.60%	44.60%
Combined ratio	109.20%	107.70%	105.90%	102.40%
Assets [Abstract]
Assets	$ 156,237		$ 156,237		167,845
Operating Segments | AmTrust Reinsurance
Net Income (Loss) [Abstract]
Gross premiums written	(5,635)	$ 21,405	(10,340)	$ (564,199)
Net premiums written	(5,635)	21,405	(10,098)	(564,199)
Total	12,982	74,406	41,447	343,730
Other insurance revenue	0	0	0	0
Net loss and loss adjustment expenses ("loss and LAE")	(2,441)	(126,945)	(21,456)	(374,103)
Commission and other acquisition expenses	(5,447)	(25,758)	(16,221)	(127,623)
General and administrative expenses	(630)	(235)	(1,941)	(2,063)
Underwriting (loss) income	$ 4,464	$ (78,532)	$ 1,829	$ (160,059)
Reconciliation to net income (loss) from continuing operations
Net loss and LAE ratio	18.80%	170.60%	51.80%	108.80%
Commission and other acquisition expense ratio	42.00%	34.60%	39.10%	37.10%
General and administrative expense ratio	4.80%	0.30%	4.70%	0.60%
Expense ratio	46.80%	34.90%	43.80%	37.70%
Combined ratio	65.60%	205.50%	95.60%	146.50%
Assets [Abstract]
Assets	$ 2,413,955		$ 2,413,955		2,843,802
Other
Net Income (Loss) [Abstract]
Gross premiums written		$ 0		$ 0
Net premiums written		0		0
Total		0		0
Other insurance revenue		0		0
Net loss and loss adjustment expenses ("loss and LAE")		(108)		(312)
Commission and other acquisition expenses		0		0
General and administrative expenses		0		0
Underwriting (loss) income		$ (108)		$ (312)
Assets [Abstract]
Assets	484,512		484,512		556,549
Other | Diversified Reinsurance
Assets [Abstract]
Assets	0		0		0
Other | AmTrust Reinsurance
Assets [Abstract]
Assets	$ 0		$ 0		$ 0