Supplemental Guarantor Condensed Consolidating Financial Statements 2011 and 2010 Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net Cash Provided by (Used in) Operating Activities	$ (56.3)	$ 240.3	$ 15.9
Investing activities
Purchases of property, plant and equipment	(163.1)	(108.3)	(137.7)
Proceeds from sale of property, plant and equipment	8.9	4.9	1.7
Purchase buyouts of leased equipment	(13.4)	(7.8)	0
Acquisition, net	(16.5)	(2.2)	(10.2)
Redemption of short-term investments	0	6.4	71.6
Net cash used in investing activities	(184.1)	(107.0)	(74.6)
Financing Activities
Net debt activity	173.6	(61.9)	(75.1)
Intercompany Activity	0	0	0
Debt issuance costs	(10.9)	(2.2)	(32.9)
Employee stock option exercises, including tax benefit	4.6	1.1	1.0
Purchase of treasury stock	(0.1)	(1.3)	(0.9)
Proceeds from issuance of common stock, net	0	0	109.7
Proceeds from issuance of warrants to GM	0	0	30.3
Purchase of noncontrolling interest	0	(2.1)	0
Net cash provided by (used in) financing activities	167.2	(66.4)	32.1
Effect of Exchange Rate on Cash and Cash Equivalents	(2.2)	(0.4)	5.9
Net increase (decrease) in cash and cash equivalents	(75.4)	66.5	(20.7)
Cash and cash equivalents at beginning of year	244.6	178.1	198.8
Cash and cash equivalents at end of year	169.2	244.6	178.1
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
Purchase buyouts of leased equipment	0	0
Acquisition, net	0	0	0
Redemption of short-term investments		0	0
Net cash used in investing activities	0	0	0
Financing Activities
Net debt activity	0	0	0
Intercompany Activity	0.1	1.3	(139.1)
Debt issuance costs	0	0	0
Employee stock option exercises, including tax benefit	0	0	0
Purchase of treasury stock	(0.1)	(1.3)	(0.9)
Proceeds from issuance of common stock, net			109.7
Proceeds from issuance of warrants to GM			30.3
Purchase of noncontrolling interest		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	(119.3)	(5.9)	(160.1)
Investing activities
Purchases of property, plant and equipment	(43.9)	(30.8)	(55.3)
Proceeds from sale of property, plant and equipment	1.5	1.7	1.4
Purchase buyouts of leased equipment	(13.4)	(7.8)
Acquisition, net	0	0	0
Redemption of short-term investments		1.6	7.9
Net cash used in investing activities	(55.8)	(35.3)	(46.0)
Financing Activities
Net debt activity	159.6	(59.2)	(65.4)
Intercompany Activity	37.9	88.5	329.4
Debt issuance costs	(10.9)	(2.2)	(32.9)
Employee stock option exercises, including tax benefit	4.6	1.1	1.0
Purchase of treasury stock	0	0	0
Proceeds from issuance of common stock, net			0
Proceeds from issuance of warrants to GM			0
Purchase of noncontrolling interest		0
Net cash provided by (used in) financing activities	191.2	28.2	232.1
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	16.1	(13.0)	26.0
Cash and cash equivalents at beginning of year	67.6	80.6	54.6
Cash and cash equivalents at end of year	83.7	67.6	80.6
Guarantor Subsidiaries of Certain Notes [Member]
Net Cash Provided by (Used in) Operating Activities	40.1	40.3	15.6
Investing activities
Purchases of property, plant and equipment	(4.9)	(6.2)	(26.3)
Proceeds from sale of property, plant and equipment	0	0	0.3
Purchase buyouts of leased equipment	0	0
Acquisition, net	(16.5)	0	(10.2)
Redemption of short-term investments		0	0
Net cash used in investing activities	(21.4)	(6.2)	(36.2)
Financing Activities
Net debt activity	(0.2)	(0.2)	(0.2)
Intercompany Activity	(18.5)	(33.7)	22.7
Debt issuance costs	0	0	0
Employee stock option exercises, including tax benefit	0	0	0
Purchase of treasury stock	0	0	0
Proceeds from issuance of common stock, net			0
Proceeds from issuance of warrants to GM			0
Purchase of noncontrolling interest		(2.1)
Net cash provided by (used in) financing activities	(18.7)	(36.0)	22.5
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	0	(1.9)	1.9
Cash and cash equivalents at beginning of year	0	1.9	0
Cash and cash equivalents at end of year	0	0	1.9
Non-Guarantor Subsidiaries [Member]
Net Cash Provided by (Used in) Operating Activities	22.9	205.9	160.4
Investing activities
Purchases of property, plant and equipment	(114.3)	(71.3)	(56.1)
Proceeds from sale of property, plant and equipment	7.4	3.2	0
Purchase buyouts of leased equipment	0	0
Acquisition, net	0	(2.2)	0
Redemption of short-term investments		4.8	63.7
Net cash used in investing activities	(106.9)	(65.5)	7.6
Financing Activities
Net debt activity	14.2	(2.5)	(9.5)
Intercompany Activity	(19.5)	(56.1)	(213.0)
Debt issuance costs	0	0	0
Employee stock option exercises, including tax benefit	0	0	0
Purchase of treasury stock	0	0	0
Proceeds from issuance of common stock, net			0
Proceeds from issuance of warrants to GM			0
Purchase of noncontrolling interest		0
Net cash provided by (used in) financing activities	(5.3)	(58.6)	(222.5)
Effect of Exchange Rate on Cash and Cash Equivalents	(2.2)	(0.4)	5.9
Net increase (decrease) in cash and cash equivalents	(91.5)	81.4	(48.6)
Cash and cash equivalents at beginning of year	177.0	95.6	144.2
Cash and cash equivalents at end of year	85.5	177.0	95.6
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
Purchase buyouts of leased equipment	0	0
Acquisition, net	0	0	0
Redemption of short-term investments		0	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
Proceeds from issuance of common stock, net			0
Proceeds from issuance of warrants to GM			0
Purchase of noncontrolling interest		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