XML 118 R104.htm IDEA: XBRL DOCUMENT v3.8.0.1
Earnings Per Share Earnings Per Share (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Numerator [Abstract]                      
Net income attributable to AAM $ 106.3 $ 86.2 $ 66.2 $ 78.4 $ 46.9 $ 61.7 $ 71.0 $ 61.1 $ 337.1 $ 240.7 $ 235.6
Less: Net income attributable to participating securities                 (7.5) (5.5) (5.3)
Net income attributable to common shareholders - Basic and Dilutive                 $ 329.6 $ 235.2 $ 230.3
Denominator [Abstract]                      
Weighted-average shares outstanding                 104.6 78.2 77.7
Less: Participating securities                 (2.3) (1.8) (1.8)
Weighted-average common shares outstanding                 102.3 76.4 75.9
Dilutive stock-based compensation                 0.5 0.5 0.4
Diluted shares outstanding - adjusted weighted-average shares after assumed conversions                 102.8 76.9 76.3
Basic earnings per share $ 0.93 $ 0.76 $ 0.59 $ 1.00 $ 0.60 $ 0.79 $ 0.91 $ 0.78 $ 3.22 $ 3.08 $ 3.03
Diluted earnings per share $ 0.93 $ 0.75 $ 0.59 $ 0.99 $ 0.59 $ 0.78 $ 0.90 $ 0.78 $ 3.21 $ 3.06 $ 3.02