Significant Accounting Policies (Details) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Unfavorable reserve development				$ 403,211,000	$ 247,175,000	$ 76,969,000
Earnings per common share, basic, reduction from unfavorable reserve development (in dollar per share)	$ 1.83	$ (2.53)	$ (1.66)	$ 4.81	$ 2.80
Earnings per common share, diluted, reduction from unfavorable reserve development (in dollar per share)				$ (4.81)	$ (2.80)
Short-term investments	$ 0			$ 0	$ 0
Deposit contracts	0			0	0
Cumulative translation adjustment	554,916,000			554,916,000	1,232,626,000	1,361,152,000
Net unrealized losses				(502,000)	0	0
Foreign currency translation adjustments, attributable to Maiden shareholders
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cumulative translation adjustment	(5,854,000)			(5,854,000)	(8,535,000)	35,713,000
AmTrust Reinsurance segment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Unfavorable reserve development	$ 151,874,000	$ (210,433,000)	$ 139,024,000	399,200,000	239,896,000	54,000,000
Maiden US Sale | Discontinued Operations, Held-for-sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Impairment of goodwill and intangible assets				$ 74,196,000	$ 0	$ 1,800,000