Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net income	$ 366.7	$ 137.1	$ 114.5
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	(58.9)	(63.5)	(50.3)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(9.4)	(27.3)	7.3
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	7.8	(6.8)	1.3
Other Comprehensive Loss, Net of Tax	(60.5)	(97.6)	(41.7)
Comprehensive Income	306.2	39.5	72.8
Net loss attributable to the noncontrolling interests	1.0	5.7	0.9
Foreign Currency Translation Adjustments Attributable to Noncontrolling Interests	0.3	0.2	(0.1)
Comprehensive Income Attributable to AAM	$ 306.9	$ 45.0	$ 73.8