Consolidated Statements of Stockholders' Equity and Other Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Paid in Capital	$ 597.2	$ 588.1	$ 597.2	$ 588.1
Accumulated Deficit	(643.5)	(786.3)	(643.5)	(786.3)
Treasury Stock	(176.2)	(176.1)	(176.2)	(176.1)
Noncontrolling interest in subsidiaries	5.9	11.4	5.9	11.4	0.3	0.2
Net income (loss) attributable to AAM	31.1	34.9	142.8	115.4	(253.1)
Net Income (Loss) Attributable to Noncontrolling Interest			(5.7)	(0.9)	(0.2)
Total Comprehensive Income (Loss)			137.1	114.5	(253.3)
Other Comprehensive Income (Loss), Change in Derivatives, net Attributable to AAM			(6.8)	1.3	11.4
Total Other Comprehensive Income (Loss), Change in Derivatives, Net			(6.8)	1.3	11.4
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Attributable to AAM			(27.5)	7.4	37.2
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, related to Noncontrolling Interest			0.2	(0.1)	0.4
Total Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment			(27.3)	7.3	37.6
Other Comprehensive Income (Loss), Defined Benefit Plans, Net Attributable to AAM			(63.5)	(50.3)	(72.5)
Total Other Comprehensive Income (Loss), Defined Benefit Plans, Net			(63.5)	(50.3)	(72.5)
Total Comprehensive Income (Loss) Attributable to AAM			45.0	73.8	(277.0)
Total Comprehensive Income (Loss) Attributable to Noncontrolling Interests			(5.5)	(1.0)	0.2
Total Comprehensive Income (Loss)			39.5	72.8	(276.8)
Issuance of Noncontrolling Interest in e-AAM				12.0
Change in additional paid in capital for purchase of noncontrolling interest				(2.1)
Decrease in noncontrolling interest due to change in ownership percentage					(0.1)
Change in Noncontrolling Interest related to acquisition of noncontrolling interest				0.1
Common Stock [Member]
Common Stock, Shares Outstanding	73.8	68.8	73.8	68.8	68.4	51.7
Common Stock, Par Value	0.8	0.8	0.8	0.8	0.8	0.6
Stock Issued During Period, Issuance of common stock					16.1
Change in Common Stock Par Value, Issuance of common stock					0.2
Stock Issued During Period, Exercise of stock options and vesting of restricted stock			1.7	0.5	0.6
Stock Issued During Period, Exercise of GM warrants			3.3
Stock Repurchased During Period, treasury stock			0	(0.1)
Additional Paid-in Capital [Member]
Paid in Capital	597.2	588.1	597.2	588.1	579.9	426.7
Adjustment to Additional Paid in Capital, Common stock issuance					109.5
Adjustments to Additional Paid in Capital from issuance of warrants to GM					30.3
Change in additional paid in capital for exercise of stock options and vesting of restricted stock			4.6	1.1	1.0
Adjustments to Additional Paid in Capital, Stock Based Compensation			4.5	9.2	12.4
Retained Earnings [Member]
Accumulated Deficit	(643.5)	(786.3)	(643.5)	(786.3)	(901.7)	(648.6)
Net income (loss) attributable to AAM			142.8	115.4	(253.1)
Treasury Stock [Member]
Treasury Stock	(176.2)	(176.1)	(176.2)	(176.1)	(174.8)	(173.9)
Adjustment to Treasury Stock, repurchase of treasury stock			(0.1)	(1.3)	(0.9)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss)	(203.8)	(106.0)	(203.8)	(106.0)	(64.4)	(40.5)
Other Comprehensive Income (Loss), Change in Derivatives, net Attributable to AAM			(6.8)	1.3	11.4
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Attributable to AAM			(27.5)	7.4	37.2
Other Comprehensive Income (Loss), Defined Benefit Plans, Net Attributable to AAM			$ (63.5)	$ (50.3)	$ (72.5)