Supplemental Guarantor Condensed Consolidating Financial Statements 2012 Income Statement (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net sales
External									$ 2,930.9	$ 2,585.0	$ 2,283.0
Intercompany									0	0	0
Total net sales	736.7	702.9	739.8	751.5	605.6	647.6	686.2	645.6	2,930.9	2,585.0	2,283.0
Cost of Goods Sold									2,531.2	2,129.9	1,881.3
Gross profit	84.0	90.7	85.8	139.2	105.7	103.5	130.5	115.4	399.7	455.1	401.7
Selling, general and administrative expenses									243.3	231.7	197.6
Operating income									156.4	223.4	204.1
Non-operating income (expense), net									(124.9)	(85.3)	(85.3)
Income (loss) before income taxes									31.5	138.1	118.8
Income Tax Expense (Benefit)									(335.2)	1.0	4.3
Earnings (loss) from equity in subsidiaries									0	0	0
Net Income (Loss) Before Royalties and Dividends									366.7	137.1	114.5
Royalties and Dividends									0	0	0
Net Income (Loss) After Royalties and Dividends									366.7	137.1	114.5
Net Income (Loss) Attributable to Noncontrolling Interest									1.0	5.7	0.9
Net income attributable to AAM	319.9	(8.1)	4.7	51.2	31.1	24.8	49.2	37.7	367.7	142.8	115.4
Other Comprehensive Income (Loss), Net of Tax									(60.5)	(97.6)	(41.7)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest									0.3	0.2	(0.1)
Comprehensive Income Attributable to AAM									306.9	45.0	73.8
Holdings [Member]
Net sales
External									0	0	0
Intercompany									0	0	0
Total net sales									0	0	0
Cost of Goods Sold									0	0	0
Gross profit									0	0	0
Selling, general and administrative expenses									0	0	0
Operating income									0	0	0
Non-operating income (expense), net									0	0	0
Income (loss) before income taxes									0	0	0
Income Tax Expense (Benefit)									0	0	0
Earnings (loss) from equity in subsidiaries									367.7	142.8	115.4
Net Income (Loss) Before Royalties and Dividends									367.7	142.8	115.4
Royalties and Dividends									0	0	0
Net Income (Loss) After Royalties and Dividends									367.7	142.8	115.4
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	0
Net income attributable to AAM									367.7	142.8	115.4
Other Comprehensive Income (Loss), Net of Tax									(60.5)	(97.6)	(41.7)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest									0.3	0.2	(0.1)
Comprehensive Income Attributable to AAM									306.9	45.0	73.8
AAM Inc. [Member]
Net sales
External									704.8	777.7	623.6
Intercompany									18.6	25.1	26.0
Total net sales									723.4	802.8	649.6
Cost of Goods Sold									709.8	727.0	601.1
Gross profit									13.6	75.8	48.5
Selling, general and administrative expenses									186.5	192.0	177.8
Operating income									(172.9)	(116.2)	(129.3)
Non-operating income (expense), net									(135.2)	(91.8)	(88.6)
Income (loss) before income taxes									(308.1)	(208.0)	(217.9)
Income Tax Expense (Benefit)									(343.9)	(5.2)	1.5
Earnings (loss) from equity in subsidiaries									79.0	165.5	152.5
Net Income (Loss) Before Royalties and Dividends									114.8	(37.3)	(66.9)
Royalties and Dividends									252.9	180.1	182.3
Net Income (Loss) After Royalties and Dividends									367.7	142.8	115.4
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	0
Net income attributable to AAM									367.7	142.8	115.4
Other Comprehensive Income (Loss), Net of Tax									(60.5)	(97.6)	(41.7)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest									0.3	0.2	(0.1)
Comprehensive Income Attributable to AAM									306.9	45.0	73.8
Guarantor Subsidiaries of Certain Notes [Member]
Net sales
External									214.4	195.3	186.7
Intercompany									226.8	189.8	160.9
Total net sales									441.2	385.1	347.6
Cost of Goods Sold									389.8	334.2	323.9
Gross profit									51.4	50.9	23.7
Selling, general and administrative expenses									0	0	0
Operating income									51.4	50.9	23.7
Non-operating income (expense), net									(2.2)	1.0	0.3
Income (loss) before income taxes									49.2	51.9	24.0
Income Tax Expense (Benefit)									(5.5)	1.2	0.3
Earnings (loss) from equity in subsidiaries									(49.2)	(37.7)	(26.8)
Net Income (Loss) Before Royalties and Dividends									5.5	13.0	(3.1)
Royalties and Dividends									0	0	0
Net Income (Loss) After Royalties and Dividends									5.5	13.0	(3.1)
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	0
Net income attributable to AAM									5.5	13.0	(3.1)
Other Comprehensive Income (Loss), Net of Tax									(10.1)	(29.0)	12.1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest									0	0	0
Comprehensive Income Attributable to AAM									(4.6)	(16.0)	9.0
Non-Guarantor Subsidiaries [Member]
Net sales
External									2,011.7	1,612.0	1,472.7
Intercompany									25.2	12.7	14.8
Total net sales									2,036.9	1,624.7	1,487.5
Cost of Goods Sold									1,702.2	1,296.3	1,158.0
Gross profit									334.7	328.4	329.5
Selling, general and administrative expenses									56.8	39.7	19.8
Operating income									277.9	288.7	309.7
Non-operating income (expense), net									12.5	5.5	3.0
Income (loss) before income taxes									290.4	294.2	312.7
Income Tax Expense (Benefit)									14.2	5.0	2.5
Earnings (loss) from equity in subsidiaries									0	0	0
Net Income (Loss) Before Royalties and Dividends									276.2	289.2	310.2
Royalties and Dividends									(252.9)	(180.1)	(182.3)
Net Income (Loss) After Royalties and Dividends									23.3	109.1	127.9
Net Income (Loss) Attributable to Noncontrolling Interest									1.0	5.7	0.9
Net income attributable to AAM									24.3	114.8	128.8
Other Comprehensive Income (Loss), Net of Tax									(3.6)	(35.6)	14.5
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest									0.3	0.2	(0.1)
Comprehensive Income Attributable to AAM									20.4	79.0	143.4
Consolidation, Eliminations [Member]
Net sales
External									0	0	0
Intercompany									(270.6)	(227.6)	(201.7)
Total net sales									(270.6)	(227.6)	(201.7)
Cost of Goods Sold									(270.6)	(227.6)	(201.7)
Gross profit									0	0	0
Selling, general and administrative expenses									0	0	0
Operating income									0	0	0
Non-operating income (expense), net									0	0	0
Income (loss) before income taxes									0	0	0
Income Tax Expense (Benefit)									0	0	0
Earnings (loss) from equity in subsidiaries									(397.5)	(270.6)	(241.1)
Net Income (Loss) Before Royalties and Dividends									(397.5)	(270.6)	(241.1)
Royalties and Dividends									0	0	0
Net Income (Loss) After Royalties and Dividends									(397.5)	(270.6)	(241.1)
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	0
Net income attributable to AAM									(397.5)	(270.6)	(241.1)
Other Comprehensive Income (Loss), Net of Tax									74.2	162.2	15.1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest									(0.6)	(0.4)	0.2
Comprehensive Income Attributable to AAM									$ (322.7)	$ (108.0)	$ (226.2)