Supplemental Guarantor Condensed Consolidating Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Cash and cash equivalents	$ 85.2	$ 169.2	$ 250.3	$ 244.6
Accounts receivable, net	474.2	333.3
Inventories, net	208.5	177.2
Other assets, current	93.7	83.4
Total current assets	861.6	763.1
Property, plant and equipment, net	990.3	971.2
Goodwill	155.9	155.9
Other assets, noncurrent, condensed	433.4	438.5
Equity method investments	0	0
Total assets	2,441.2	2,328.7
Accounts payable	439.6	337.1
Other liabilities, current, condensed	252.3	239.0
Total current liabilities	691.9	576.1
Intercompany payable (receivable)	0	0
Long-term debt	1,174.3	1,180.2
Investment in subsidiaries obligation	0	0
Other liabilities, noncurrent	969.7	992.0
Total liabilities	2,835.9	2,748.3
Total AAM stockholders' deficit	(394.7)	(425.5)
Noncontrolling interest in subsidiaries	0	5.9
Total stockholders’ deficit	(394.7)	(419.6)
Total liabilities and stockholders' deficit	2,441.2	2,328.7
Holdings [Member]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Inventories, net	0	0
Other assets, current	0	0
Total current assets	0	0
Property, plant and equipment, net	0	0
Goodwill	0	0
Other assets, noncurrent, condensed	0	0
Equity method investments	0	0
Total assets	0	0
Accounts payable	0	0
Other liabilities, current, condensed	0	0
Total current liabilities	0	0
Intercompany payable (receivable)	326.6	320.7
Long-term debt	0	0
Investment in subsidiaries obligation	68.1	104.8
Other liabilities, noncurrent	0	0
Total liabilities	394.7	425.5
Total AAM stockholders' deficit	(394.7)	(425.5)
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	(394.7)	(425.5)
Total liabilities and stockholders' deficit	0	0
AAM Inc. [Member]
Cash and cash equivalents	22.4	83.7	62.0	67.6
Accounts receivable, net	106.2	77.1
Inventories, net	43.6	48.2
Other assets, current	22.5	26.5
Total current assets	194.7	235.5
Property, plant and equipment, net	261.6	260.4
Goodwill	0	0
Other assets, noncurrent, condensed	318.0	327.2
Equity method investments	1,109.5	1,015.2
Total assets	1,883.8	1,838.3
Accounts payable	103.9	96.3
Other liabilities, current, condensed	162.2	155.1
Total current liabilities	266.1	251.4
Intercompany payable (receivable)	(350.4)	(368.6)
Long-term debt	1,129.2	1,128.9
Investment in subsidiaries obligation	0	0
Other liabilities, noncurrent	907.0	931.4
Total liabilities	1,951.9	1,943.1
Total AAM stockholders' deficit	(68.1)	(104.8)
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	(68.1)	(104.8)
Total liabilities and stockholders' deficit	1,883.8	1,838.3
Guarantor Subsidiaries of Certain Notes [Member]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	28.0	23.3
Inventories, net	30.6	35.3
Other assets, current	1.4	1.7
Total current assets	60.0	60.3
Property, plant and equipment, net	83.7	84.6
Goodwill	147.8	147.8
Other assets, noncurrent, condensed	38.5	35.8
Equity method investments	4.6	26.6
Total assets	334.6	355.1
Accounts payable	45.8	41.0
Other liabilities, current, condensed	3.8	3.0
Total current liabilities	49.6	44.0
Intercompany payable (receivable)	270.9	289.0
Long-term debt	5.8	5.9
Investment in subsidiaries obligation	0	0
Other liabilities, noncurrent	3.6	3.6
Total liabilities	329.9	342.5
Total AAM stockholders' deficit	4.7	12.6
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	4.7	12.6
Total liabilities and stockholders' deficit	334.6	355.1
Non-Guarantor Subsidiaries [Member]
Cash and cash equivalents	62.8	85.5	188.3	177.0
Accounts receivable, net	340.0	232.9
Inventories, net	134.3	93.7
Other assets, current	69.8	55.2
Total current assets	606.9	467.3
Property, plant and equipment, net	645.0	626.2
Goodwill	8.1	8.1
Other assets, noncurrent, condensed	76.9	75.5
Equity method investments	0	0
Total assets	1,336.9	1,177.1
Accounts payable	289.9	199.8
Other liabilities, current, condensed	86.3	80.9
Total current liabilities	376.2	280.7
Intercompany payable (receivable)	(247.1)	(241.1)
Long-term debt	39.3	45.4
Investment in subsidiaries obligation	0	0
Other liabilities, noncurrent	59.1	57.0
Total liabilities	227.5	142.0
Total AAM stockholders' deficit	1,109.4	1,029.2
Noncontrolling interest in subsidiaries	0	5.9
Total stockholders’ deficit	1,109.4	1,035.1
Total liabilities and stockholders' deficit	1,336.9	1,177.1
Consolidation, Eliminations [Member]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Inventories, net	0	0
Other assets, current	0	0
Total current assets	0	0
Property, plant and equipment, net	0	0
Goodwill	0	0
Other assets, noncurrent, condensed	0	0
Equity method investments	(1,114.1)	(1,041.8)
Total assets	(1,114.1)	(1,041.8)
Accounts payable	0	0
Other liabilities, current, condensed	0	0
Total current liabilities	0	0
Intercompany payable (receivable)	0	0
Long-term debt	0	0
Investment in subsidiaries obligation	(68.1)	(104.8)
Other liabilities, noncurrent	0	0
Total liabilities	(68.1)	(104.8)
Total AAM stockholders' deficit	(1,046.0)	(937.0)
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	(1,046.0)	(937.0)
Total liabilities and stockholders' deficit	$ (1,114.1)	$ (1,041.8)

This element represents the net payables/(receivables) arising from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, such as pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's' management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

No definition available.