v2.4.0.8
Segments - Net Premiums (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Segment Reporting Information [Line Items]        
Net premiums written $ 497,949 $ 411,960 $ 1,187,008 $ 1,002,793
% of Total Net premiums written 100.00% 100.00% 100.00% 100.00%
Net premiums earned 513,273 437,116 1,001,715 875,612
% of Total Net premiums earned 100.00% 100.00% 100.00% 100.00%
Diversified Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 134,934 143,981 402,544 432,277
% of Total Net premiums written 27.00% 34.90% 33.90% 43.10%
Net premiums earned 178,336 199,130 374,585 403,593
% of Total Net premiums earned 34.80% 45.60% 37.40% 46.10%
AmTrust Quota Share Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 290,578 195,629 635,396 421,644
% of Total Net premiums written 58.40% 47.50% 53.50% 42.10%
Net premiums earned 261,404 167,816 481,692 335,695
% of Total Net premiums earned 50.90% 38.30% 48.10% 38.30%
NGHC Quota Share Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 72,437 72,350 149,068 148,872
% of Total Net premiums written 14.60% 17.60% 12.60% 14.80%
Net premiums earned 73,533 70,170 145,438 136,324
% of Total Net premiums earned 14.30% 16.10% 14.50% 15.60%
Property [Member] | Diversified Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 16,556 35,855 86,078 115,961
% of Total Net premiums written 3.30% 8.70% 7.30% 11.60%
Net premiums earned 27,771 55,903 75,318 114,051
% of Total Net premiums earned 5.40% 12.80% 7.50% 13.00%
Casualty [Member] | Diversified Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 88,793 82,762 237,216 234,701
% of Total Net premiums written 17.80% 20.10% 20.00% 23.40%
Net premiums earned 116,838 111,008 233,897 214,987
% of Total Net premiums earned 22.80% 25.40% 23.40% 24.60%
Accident and Health [Member] | Diversified Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 7,080 5,838 22,609 25,310
% of Total Net premiums written 1.40% 1.40% 1.80% 2.50%
Net premiums earned 9,729 10,727 18,362 21,371
% of Total Net premiums earned 1.90% 2.50% 1.80% 2.40%
International [Member] | Diversified Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 22,505 19,526 56,641 56,305
% of Total Net premiums written 4.50% 4.70% 4.80% 5.60%
Net premiums earned 23,998 21,492 47,008 53,184
% of Total Net premiums earned 4.70% 4.90% 4.70% 6.10%
Small Commercial Business [Member] | AmTrust Quota Share Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 136,208 81,882 298,226 172,174
% of Total Net premiums written 27.40% 19.90% 25.10% 17.20%
Net premiums earned 117,566 69,907 219,823 136,799
% of Total Net premiums earned 22.90% 16.00% 22.00% 15.60%
Specialty Program [Member] | AmTrust Quota Share Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 38,669 26,758 73,615 48,946
% of Total Net premiums written 7.80% 6.50% 6.20% 4.90%
Net premiums earned 32,115 22,948 65,461 50,586
% of Total Net premiums earned 6.20% 5.20% 6.50% 5.80%
Specialty Risk and Extended Warranty [Member] | AmTrust Quota Share Reinsurance Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 115,701 86,989 263,555 200,524
% of Total Net premiums written 23.20% 21.10% 22.20% 20.00%
Net premiums earned 111,723 74,961 196,408 148,310
% of Total Net premiums earned 21.80% 17.10% 19.60% 16.90%
Automobile Liability [Member] | NGHC Quota Share Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 41,585 35,401 85,924 79,269
% of Total Net premiums written 8.40% 8.60% 7.20% 7.90%
Net premiums earned 42,473 36,657 84,103 74,794
% of Total Net premiums earned 8.30% 8.40% 8.40% 8.60%
Automobile Physical Damage [Member] | NGHC Quota Share Segment [Member]
       
Segment Reporting Information [Line Items]        
Net premiums written 30,852 36,949 63,144 69,603
% of Total Net premiums written 6.20% 9.00% 5.40% 6.90%
Net premiums earned $ 31,060 $ 33,513 $ 61,335 $ 61,530
% of Total Net premiums earned 6.00% 7.70% 6.10% 7.00%