v3.3.1.900
Segment Information - Net Premiums (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Segment Reporting, Revenue Reconciling Item [Line Items]      
Gross premiums written $ 2,662,825 $ 2,507,352 $ 2,204,159
Net premiums written 2,514,116 2,458,136 2,096,301
Net premiums earned $ 2,429,069 $ 2,251,743 $ 2,000,887
% of Total Net premiums written 100.00% 100.00% 100.00%
% of Total Net premiums earned 100.00% 100.00% 100.00%
Diversified Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Gross premiums written $ 776,852 $ 897,748 $ 848,790
Net premiums written 734,781 850,049 763,374
Net premiums earned $ 744,875 $ 854,026 $ 753,157
% of Total Net premiums written 29.20% 34.60% 36.40%
% of Total Net premiums earned 30.70% 37.90% 37.60%
AmTrust Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Gross premiums written $ 1,885,974 $ 1,610,485 $ 1,169,961
Net premiums written 1,779,334 1,610,485 1,169,961
Net premiums earned $ 1,684,191 $ 1,378,327 $ 988,900
% of Total Net premiums written 70.80% 65.50% 55.80%
% of Total Net premiums earned 69.30% 61.20% 49.40%
Other      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Gross premiums written $ (1) $ (881) $ 185,408
Net premiums written 1 (2,398) 162,966
Net premiums earned $ 3 $ 19,390 $ 258,830
% of Total Net premiums written 0.00% (0.10%) 7.80%
% of Total Net premiums earned 0.00% 0.90% 13.00%
Property | Diversified Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net premiums written $ 160,939 $ 160,308 $ 145,292
Net premiums earned $ 157,186 $ 174,785 $ 150,261
% of Total Net premiums written 6.40% 6.50% 6.90%
% of Total Net premiums earned 6.50% 7.70% 7.50%
Casualty | Diversified Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net premiums written $ 435,625 $ 535,518 $ 473,732
Net premiums earned $ 449,000 $ 533,775 $ 472,095
% of Total Net premiums written 17.30% 21.80% 22.60%
% of Total Net premiums earned 18.50% 23.70% 23.60%
Accident and Health | Diversified Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net premiums written $ 64,102 $ 38,870 $ 35,340
Net premiums earned $ 55,672 $ 39,918 $ 36,165
% of Total Net premiums written 2.60% 1.60% 1.70%
% of Total Net premiums earned 2.30% 1.80% 1.80%
International | Diversified Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net premiums written $ 74,115 $ 115,353 $ 109,010
Net premiums earned $ 83,017 $ 105,548 $ 94,636
% of Total Net premiums written 2.90% 4.70% 5.20%
% of Total Net premiums earned 3.40% 4.70% 4.70%
Small Commercial Business | AmTrust Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net premiums written $ 1,057,968 $ 857,576 $ 572,006
Net premiums earned $ 984,333 $ 752,188 $ 493,774
% of Total Net premiums written 42.10% 34.90% 27.30%
% of Total Net premiums earned 40.50% 33.40% 24.70%
Specialty Program | AmTrust Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net premiums written $ 332,416 $ 220,121 $ 157,578
Net premiums earned $ 290,209 $ 175,286 $ 140,478
% of Total Net premiums written 13.20% 8.90% 7.50%
% of Total Net premiums earned 11.90% 7.80% 7.00%
Specialty Risk and Extended Warranty | AmTrust Reinsurance segment      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net premiums written $ 388,950 $ 532,788 $ 440,377
Net premiums earned $ 409,649 $ 450,853 $ 354,648
% of Total Net premiums written 15.50% 21.70% 21.00%
% of Total Net premiums earned 16.90% 20.00% 17.70%
North America      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Gross premiums written $ 2,165,309 $ 1,979,768 $ 1,742,333
Net premiums written 2,038,444 1,934,644 1,638,844
Net premiums earned 2,027,141 1,778,579 1,602,128
Other (predominantly Europe)      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Gross premiums written 497,516 527,584 461,826
Net premiums written 475,672 523,492 457,457
Net premiums earned $ 401,928 $ 473,164 $ 398,759