v2.4.0.6
Summary of Elements Used in Calculating Basic and Diluted Earnings Per Share (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Basic earnings per share:        
Net income attributable to AmTrust Financial Services, Inc. shareholders $ 40,358 $ 50,162 $ 79,444 $ 95,345
Less: Net income allocated to participating securities and redeemable non-controlling interest 182 39 197 64
Net income allocated to AmTrust Financial Services, Inc. common shareholders 40,176 50,123 79,247 95,281
Weighted average common shares outstanding - basic 60,649 59,880 60,345 59,766
Less: Weighted average participating shares outstanding 273 36 150 42
Weighted average common shares outstanding - basic 60,376 59,844 60,195 59,724
Net income per AmTrust Financial Services, Inc. common share - basic $ 0.67 $ 0.84 $ 1.32 $ 1.60
Diluted earnings per share:        
Net income attributable to AmTrust Financial Services, Inc. shareholders 40,358 50,162 79,444 95,345
Less: Net income allocated to participating securities and redeemable non-controlling interest 182 39 197 64
Net income allocated to AmTrust Financial Services, Inc. common shareholders $ 40,176 $ 50,123 $ 79,247 $ 95,281
Weighted average common shares outstanding - basic 60,376 59,844 60,195 59,724
Plus: Dilutive effect of stock options, other 2,124 1,778 2,086 1,670
Weighted average common shares outstanding - dilutive 62,500 61,622 62,281 61,394
Net income per AmTrust Financial Services, Inc. common shares - diluted $ 0.64 $ 0.81 $ 1.27 $ 1.55