v3.8.0.1
Related Party Transactions - AmTrust (Details)
3 Months Ended 9 Months Ended
Jul. 01, 2016
Apr. 01, 2012
USD ($)
Jan. 01, 2012
EUR (€)
Apr. 01, 2011
EUR (€)
Mar. 01, 2011
Sep. 01, 2010
Jun. 11, 2008
Jul. 01, 2007
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
Dec. 31, 2016
USD ($)
Jun. 23, 2008
USD ($)
Apr. 11, 2008
USD ($)
Dec. 18, 2007
USD ($)
Related Party Transaction [Line Items]                                
Net premiums earned                 $ 653,866,000 $ 698,278,000 $ 2,074,475,000 $ 1,951,851,000        
Loan to related party                 $ 167,975,000   $ 167,975,000   $ 167,975,000      
Leah Karfunkel                                
Related Party Transaction [Line Items]                                
Noncontrolling interest, ownership percentage                 8.00%   8.00%          
Leah Karfunkel | National General Holdings Corp.                                
Related Party Transaction [Line Items]                                
Noncontrolling interest, ownership percentage                 41.80%   41.80%          
Barry Zyskind                                
Related Party Transaction [Line Items]                                
Noncontrolling interest, ownership percentage                 7.60%   7.60%          
George Karfunkel, less than 5% ownership                                
Related Party Transaction [Line Items]                                
Noncontrolling interest, ownership percentage                 5.00%   5.00%          
Founding shareholders | AmTrust Financial Services, Inc.                                
Related Party Transaction [Line Items]                                
Controlling interest, ownership percentage                 42.80%   42.80%          
AmTrust Financial Services, Inc.                                
Related Party Transaction [Line Items]                                
Loan to related party                 $ 167,975,000   $ 167,975,000   $ 167,975,000 $ 34,240,000 $ 20,193,000 $ 113,542,000
AmTrust Financial Services, Inc. | London Interbank Offered Rate (LIBOR)                                
Related Party Transaction [Line Items]                                
Basis spread on variable rate                 0.90%   0.90%   0.90%      
AmTrust Financial Services, Inc. | Quota Share Reinsurance Agreements | Commission expense                                
Related Party Transaction [Line Items]                                
Expenses recorded from related party transactions                 $ 138,171,000 163,336,000 $ 460,667,000 447,767,000        
AmTrust Financial Services, Inc. | AmTrust Quota Share Reinsurance Agreement                                
Related Party Transaction [Line Items]                                
Percent of premiums written, net of cost of unaffiliated inuring reinsurance from related party               40.00%                
Percent of losses with respect to current lines of business, excluding those above covered business threshold to related party               40.00%                
Commission rate, percent of ceded written premiums             34.375% 31.00%                
Contract extension (in years) 3 years                              
Cancellation notice period 9 months                              
Cancellation notice period upon the occurrence of certain early termination events (in days) 30 days                              
Early termination events, reduction threshold of stockholders' equity 50.00%                              
AmTrust Financial Services, Inc. | AmTrust Quota Share Reinsurance Agreement | Minimum                                
Related Party Transaction [Line Items]                                
Commission rate, adjustment criteria, loss ratio floor               81.50%                
AmTrust Financial Services, Inc. | AmTrust Quota Share Reinsurance Agreement | Maximum                                
Related Party Transaction [Line Items]                                
Commission rate, adjustment criteria, loss ratio ceiling               95.00%                
AmTrust Financial Services, Inc. | AmTrust European Hospital Liability Quota Share Agreement                                
Related Party Transaction [Line Items]                                
Commission rate, percent of ceded written premiums       5.00%                        
Premiums and losses related to policies 32.50%     40.00%                        
Maximum limit of liability attaching | €     € 10,000,000 € 5,000,000                        
Percent basis currency equivalent of maximum limit of liability attaching       100.00%                        
Future premiums and losses related to policies 20.00%                              
AmTrust Financial Services, Inc. | AmTrust Technology Reinsurance Agreement                                
Related Party Transaction [Line Items]                                
Commission rate, percent of ceded written premiums           5.00%                    
Percent of credit insurance business to cede           90.00%                    
Percent of general liability business to cede           100.00%                    
AmTrust Financial Services, Inc. | AmTrust Technology Reinsurance Agreement | Premiums Earned                                
Related Party Transaction [Line Items]                                
Revenue from related parties                 1,000 0 4,000 12,000        
AmTrust Financial Services, Inc. | AmTrust NA Reinsurance Agreement                                
Related Party Transaction [Line Items]                                
Agreement period (in years)   1 year                            
Reinsurance coverage threshold   $ 1,000,000                            
Net premiums earned                 351,000 305,000 1,182,000 745,000        
AmTrust Financial Services, Inc. | AmTrust NA Reinsurance Agreement | Commission expense                                
Related Party Transaction [Line Items]                                
Expenses recorded from related party transactions                 53,000 87,000 256,000 187,000        
AmTrust Financial Services, Inc. | Reinsurer Trust Assets Collateral Agreement                                
Related Party Transaction [Line Items]                                
Collateral held by related party                 3,245,369,000   3,245,369,000   $ 2,766,032,000      
Accrued interest on collateral held by related party                 21,288,000   21,288,000   20,420,000      
AmTrust Financial Services, Inc. | Reinsurance Brokerage Agreements                                
Related Party Transaction [Line Items]                                
Cancellation notice period               30 days                
Brokerage fee, percent of premium assumed               1.25%                
AmTrust Financial Services, Inc. | Reinsurance Brokerage Agreements | Brokerage expense                                
Related Party Transaction [Line Items]                                
Expenses recorded from related party transactions                 5,642,000 6,652,000 18,662,000 18,330,000        
Balances due to related party                 15,476,000   15,476,000   $ 14,395,000      
AmTrust Financial Services, Inc. | Insurance Intermediary | Brokerage expense                                
Related Party Transaction [Line Items]                                
Expenses recorded from related party transactions                 54,000 41,000 55,000 42,000        
AmTrust Financial Services, Inc. | Asset Management Agreement                                
Related Party Transaction [Line Items]                                
Cancellation notice period               30 days                
Quarterly brokerage fee, above portfolio threshold, percent of average holdings               0.0375%                
Quarterly brokerage fee, portfolio threshold               $ 1,000,000,000                
AmTrust Financial Services, Inc. | Asset Management Agreement | Investment Management Fee                                
Related Party Transaction [Line Items]                                
Expenses recorded from related party transactions                 1,927,000 1,780,000 5,586,000 5,122,000        
AmTrust Financial Services, Inc. | AmTrust Time Sharing Agreement                                
Related Party Transaction [Line Items]                                
Contract extension (in years)         1 year                      
AmTrust Financial Services, Inc. | AmTrust Time Sharing Agreement | Aircraft expenses                                
Related Party Transaction [Line Items]                                
Expenses recorded from related party transactions                 $ 0 $ 22,000 $ 39,000 $ 61,000        
AmTrust Financial Services, Inc. | National General Holdings Corp.                                
Related Party Transaction [Line Items]                                
Noncontrolling interest, ownership percentage                 1.60%   1.60%