Supplemental Guarantor Condensed Consolidating Financial Statements 2012 and 2011 Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net Cash Provided by (Used in) Operating Activities	$ (175.5)	$ (56.3)	$ 240.3
Investing activities
Purchases of property, plant and equipment	(207.6)	(163.1)	(108.3)
Proceeds from sale of property, plant and equipment	10.1	8.9	4.9
Sale Leaseback Transaction, Net Proceeds	12.1	0	0
Purchase buyouts of leased equipment	0	(13.4)	(7.8)
Acquisition, net		(16.5)	(2.2)
Redemption of short-term investments	0	0	6.4
Net cash used in investing activities	(185.4)	(184.1)	(107.0)
Financing Activities
Net debt activity	273.9	173.6	(61.9)
Intercompany Activity	0	0	0
Debt issuance costs	(10.6)	(10.9)	(2.2)
Employee stock option exercises, including tax benefit	0.1	4.6	1.1
Purchase of treasury stock	(5.9)	(0.1)	(1.3)
Purchase of noncontrolling interest	(4.0)	0	(2.1)
Net cash provided by (used in) financing activities	253.5	167.2	(66.4)
Effect of Exchange Rate on Cash and Cash Equivalents	0.6	(2.2)	(0.4)
Net increase (decrease) in cash and cash equivalents	(106.8)	(75.4)	66.5
Cash and cash equivalents at beginning of year	169.2	244.6	178.1
Cash and cash equivalents at end of year	62.4	169.2	244.6
Holdings [Member]
Net Cash Provided by (Used in) Operating Activities	0	0	0
Investing activities
Purchases of property, plant and equipment	0	0	0
Proceeds from sale of property, plant and equipment	0	0	0
Sale Leaseback Transaction, Net Proceeds	0
Purchase buyouts of leased equipment		0	0
Acquisition, net		0	0
Redemption of short-term investments			0
Net cash used in investing activities	0	0	0
Financing Activities
Net debt activity	0	0	0
Intercompany Activity	5.9	0.1	1.3
Debt issuance costs	0	0	0
Employee stock option exercises, including tax benefit	0	0	0
Purchase of treasury stock	(5.9)	(0.1)	(1.3)
Purchase of noncontrolling interest	0		0
Net cash provided by (used in) financing activities	0	0	0
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of year	0	0	0
Cash and cash equivalents at end of year	0	0	0
AAM Inc. [Member]
Net Cash Provided by (Used in) Operating Activities	(228.2)	(119.3)	(5.9)
Investing activities
Purchases of property, plant and equipment	(59.4)	(43.9)	(30.8)
Proceeds from sale of property, plant and equipment	7.0	1.5	1.7
Sale Leaseback Transaction, Net Proceeds	12.1
Purchase buyouts of leased equipment		(13.4)	(7.8)
Acquisition, net		0	0
Redemption of short-term investments			1.6
Net cash used in investing activities	(40.3)	(55.8)	(35.3)
Financing Activities
Net debt activity	257.9	159.6	(59.2)
Intercompany Activity	(52.0)	37.9	88.5
Debt issuance costs	(10.6)	(10.9)	(2.2)
Employee stock option exercises, including tax benefit	0.1	4.6	1.1
Purchase of treasury stock	0	0	0
Purchase of noncontrolling interest	0		0
Net cash provided by (used in) financing activities	195.4	191.2	28.2
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	(73.1)	16.1	(13.0)
Cash and cash equivalents at beginning of year	83.7	67.6	80.6
Cash and cash equivalents at end of year	10.6	83.7	67.6
Guarantor Subsidiaries of Certain Notes [Member]
Net Cash Provided by (Used in) Operating Activities	56.8	40.1	40.3
Investing activities
Purchases of property, plant and equipment	(9.0)	(4.9)	(6.2)
Proceeds from sale of property, plant and equipment	0	0	0
Sale Leaseback Transaction, Net Proceeds	0
Purchase buyouts of leased equipment		0	0
Acquisition, net		(16.5)	0
Redemption of short-term investments			0
Net cash used in investing activities	(9.0)	(21.4)	(6.2)
Financing Activities
Net debt activity	(0.2)	(0.2)	(0.2)
Intercompany Activity	(47.6)	(18.5)	(33.7)
Debt issuance costs	0	0	0
Employee stock option exercises, including tax benefit	0	0	0
Purchase of treasury stock	0	0	0
Purchase of noncontrolling interest	0		(2.1)
Net cash provided by (used in) financing activities	(47.8)	(18.7)	(36.0)
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	0	0	(1.9)
Cash and cash equivalents at beginning of year	0	0	1.9
Cash and cash equivalents at end of year	0	0	0
Non-Guarantor Subsidiaries [Member]
Net Cash Provided by (Used in) Operating Activities	(4.1)	22.9	205.9
Investing activities
Purchases of property, plant and equipment	(139.2)	(114.3)	(71.3)
Proceeds from sale of property, plant and equipment	3.1	7.4	3.2
Sale Leaseback Transaction, Net Proceeds	0
Purchase buyouts of leased equipment		0	0
Acquisition, net		0	(2.2)
Redemption of short-term investments			4.8
Net cash used in investing activities	(136.1)	(106.9)	(65.5)
Financing Activities
Net debt activity	16.2	14.2	(2.5)
Intercompany Activity	93.7	(19.5)	(56.1)
Debt issuance costs	0	0	0
Employee stock option exercises, including tax benefit	0	0	0
Purchase of treasury stock	0	0	0
Purchase of noncontrolling interest	(4.0)		0
Net cash provided by (used in) financing activities	105.9	(5.3)	(58.6)
Effect of Exchange Rate on Cash and Cash Equivalents	0.6	(2.2)	(0.4)
Net increase (decrease) in cash and cash equivalents	(33.7)	(91.5)	81.4
Cash and cash equivalents at beginning of year	85.5	177.0	95.6
Cash and cash equivalents at end of year	51.8	85.5	177.0
Consolidation, Eliminations [Member]
Net Cash Provided by (Used in) Operating Activities	0	0	0
Investing activities
Purchases of property, plant and equipment	0	0	0
Proceeds from sale of property, plant and equipment	0	0	0
Sale Leaseback Transaction, Net Proceeds	0
Purchase buyouts of leased equipment		0	0
Acquisition, net		0	0
Redemption of short-term investments			0
Net cash used in investing activities	0	0	0
Financing Activities
Net debt activity	0	0	0
Intercompany Activity	0	0	0
Debt issuance costs	0	0	0
Employee stock option exercises, including tax benefit	0	0	0
Purchase of treasury stock	0	0	0
Purchase of noncontrolling interest	0		0
Net cash provided by (used in) financing activities	0	0	0
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of year	0	0	0
Cash and cash equivalents at end of year	$ 0	$ 0	$ 0