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 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Basic earnings per share:        
Net income attributable to AmTrust Financial Services, Inc. shareholders $ 43,230 $ 37,166 $ 122,674 $ 132,511
Less: Net income allocated to participating securities and redeemable non-controlling interest 206 16 513 80
Net income allocated to AmTrust Financial Services, Inc. common shareholders 43,024 37,150 122,161 132,431
Weighted average common shares outstanding - basic (in shares) 62,642 61,700 61,156 60,414
Less: Weighted average participating shares outstanding (in shares) 297 32 255 40
Weighted average common shares outstanding - basic (in shares) 62,345 61,668 60,901 60,374
Net income per AmTrust Financial Services, Inc. common share - basic (usd per share) $ 0.69 $ 0.60 $ 2.01 $ 2.19
Diluted earnings per share:        
Net income attributable to AmTrust Financial Services, Inc. shareholders 43,230 37,166 122,674 132,511
Less: Net income allocated to participating securities and redeemable non-controlling interest 206 16 513 80
Net income allocated to AmTrust Financial Services, Inc. common shareholders $ 43,024 $ 37,150 $ 122,161 $ 132,431
Weighted average common shares outstanding - basic (in shares) 62,345 61,668 60,901 60,374
Plus: Dilutive effect of stock options, other (in shares) 2,779 1,984 2,515 1,719
Weighted average common shares outstanding - dilutive (in shares) 65,124 63,652 63,416 62,093
Net income per AmTrust Financial Services, Inc. common shares - diluted (usd per share) $ 0.66 $ 0.58 $ 1.93 $ 2.13