v3.19.2
Reserve for Loss and Loss Adjustment Expenses (Details) - USD ($)
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Jun. 30, 2019
Dec. 31, 2018
Insurance [Abstract]              
Reserve for reported loss and LAE           $ 1,533,380,000 $ 1,571,217,000
Reserve for losses incurred but not reported (IBNR)           1,517,885,000 1,484,759,000
Reserve for loss and LAE $ 3,051,265,000 $ 2,541,975,000 $ 3,055,976,000 $ 2,386,722,000 $ 3,055,976,000 $ 3,051,265,000 $ 3,055,976,000
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]              
Gross loss and LAE reserves, January 1     3,055,976,000 2,386,722,000 2,386,722,000    
Less: reinsurance recoverable on unpaid losses, January 1     1,743,000 24,883,000 24,883,000    
Net loss and LAE reserves, January 1     3,054,233,000 2,361,839,000 2,361,839,000    
Net incurred losses related to Current year     240,978,000 685,229,000      
Net incurred losses related to Prior years     33,272,000 37,978,000      
Net loss and loss adjustment expenses 121,561,000 370,001,000 274,250,000 723,207,000      
Net paid losses related to Current year     (3,186,000) (151,527,000)      
Net paid losses related to Prior years     (272,136,000) (401,039,000)      
Net paid losses     (275,322,000) (552,566,000)      
Effect of foreign exchange rate movements     (3,880,000) (12,308,000)      
Net loss and LAE reserves, June 30 3,049,281,000 2,520,172,000 3,049,281,000 2,520,172,000 3,054,233,000    
Reinsurance recoverable on unpaid losses, June 30 1,984,000 21,803,000 1,984,000 21,803,000 1,743,000    
Gross loss and LAE reserves, June 30 3,051,265,000 2,541,975,000 3,051,265,000 2,541,975,000 3,055,976,000    
Segment Reporting Information [Line Items]              
Net adverse prior year development (net favorable prior year reserve development) 26,014,000 28,193,000 (33,272,000) 37,978,000      
Other              
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]              
Net loss and loss adjustment expenses (24,000) 0 204,000 0      
Segment Reporting Information [Line Items]              
Net adverse prior year development (net favorable prior year reserve development) (24,000)   204,000   $ 0    
Diversified Reinsurance              
Segment Reporting Information [Line Items]              
Net adverse prior year development (net favorable prior year reserve development) (1,052,000) (181,000) (2,148,000) 1,085,000      
AmTrust Reinsurance              
Segment Reporting Information [Line Items]              
Net adverse prior year development (net favorable prior year reserve development) $ 27,090,000 $ 28,374,000 $ 35,216,000 $ (36,893,000)