v3.8.0.1

Commitments and Contingencies (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Aug. 03, 2017 | Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Loss Contingencies [Line Items] |  |  |  |  |  |
Gross premiums written |  | $ 630,972 | $ 706,854 | $ 2,259,597 | $ 2,259,290 |
Dividends declared per common share (in dollars per share) | $ 0.15 | $ 0.15 | $ 0.14 | $ 0.45 | $ 0.42 |
AmTrust Reinsurance segment [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Gross premiums written |  | $ 420,019 | $ 520,104 | $ 1,575,677 | $ 1,591,902 |
Segment concentration risk [Member] | Gross premiums written [Member] | AmTrust Reinsurance segment [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  | 66.60% | 73.60% | 69.70% | 70.50% |
Major customer one [Member] | Customer concentration risk [Member] | Reinsurance Recoverable [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  |  |  | 44.70% |  | 54.80%
Major customer two [Member] | Customer concentration risk [Member] | Reinsurance Recoverable [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  |  |  | 15.70% |  | 31.60%
Major customer three [Member] | Customer concentration risk [Member] | Reinsurance Recoverable [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  |  |  | 14.60% |  | 2.90%
Rating A or better [Member] | Customer concentration risk [Member] | Reinsurance Recoverable [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  |  |  | 98.70% |  | 97.20%
Rating B Plus Plus or lower [Member] | Customer concentration risk [Member] | Reinsurance Recoverable [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  |  |  | 1.30% |  | 2.80%
Concentration risk, collateralized, percentage |  |  |  | 89.10% |  | 98.60%

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