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Earnings Per Share (Details) (USD $)
In Millions, except Per Share data, unless otherwise specified
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Mar. 31, 2011
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2009
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]            
Net income (loss) attributable to AAM $ (8.1) $ 24.8   $ 47.8 $ 111.7  
Weighted average number of shares outstanding, basic 74.9 75.4   75.2 74.8  
Incremental Common Shares Attributable to Share-based Payment Arrangements 0 0   0 0.1  
Incremental Common Shares Attributable to Call Options and Warrants 0 0   0 0.5  
Weighted average number of shares outstanding, diluted 74.9 75.4   75.2 75.4  
Basic earnings (loss) per share $ (0.11) $ 0.33   $ 0.64 $ 1.49  
Diluted earnings (loss) per share $ (0.11) $ 0.33   $ 0.63 $ 1.48  
Earnings per share, Stock Options excluded from the calculation of diluted EPS 3.3 4.1   3.3 4.1  
Earnings per share, range of exercise prices of Stock Options excluded from the calculation of diluted EPS, lower end of range $ 15.58 $ 15.56   $ 15.58 $ 15.56  
Earnings per share, range of exercise prices of Stock Options excluded from the calculation of diluted EPS, upper end of range $ 40.83 $ 40.83   $ 40.83 $ 40.83  
Shares Exlcuded from EPS Calculation During Periods of Loss 1.0          
2009 GM Agreement, number of shares available for purchase through exercise of warrants           4.1
2009 GM Agreement, exercise price of warrants issued to GM           $ 2.76
2009 GM Agreement, shares issued to GM through exercise of warrants     3.3