Supplemental Guarantor Condensed Consolidating Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Current Assets
Cash and cash equivalents	$ 100.8	$ 62.4	$ 112.8	$ 169.2
Accounts receivable, net	535.3	463.4
Inventories, net	240.6	224.3
Other current assets	128.4	122.0
Total current assets	1,005.1	872.1
Property, plant and equipment, net	1,043.5	1,009.7
Goodwill	156.4	156.4
Other assets and deferred charges, condensed	824.6	827.8
Investment in subsidiaries	0	0
Total assets	3,029.6	2,866.0
Current Liabilities
Accounts payable	454.6	396.1
Other current liabilities	196.5	204.7
Total current liabilities	651.1	600.8
Intercompany payable (receivable)	0	0
Long-term debt	1,570.2	1,454.1
Investment in subsidiaries obligation		0
Other long-term liabilities	916.2	931.9
Total liabilities	3,137.5	2,986.8
Total AAM stockholders' deficit	(107.9)	(120.8)
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	(107.9)	(120.8)
Total liabilities and stockholders' deficit	3,029.6	2,866.0
Holdings [Member]
Current Assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Inventories, net	0	0
Other current assets	0	0
Total current assets	0	0
Property, plant and equipment, net	0	0
Goodwill	0	0
Other assets and deferred charges, condensed	0	0
Investment in subsidiaries	215.8	202.9
Total assets	215.8	202.9
Current Liabilities
Accounts payable	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Intercompany payable (receivable)	323.7	323.7
Long-term debt	0	0
Investment in subsidiaries obligation		0
Other long-term liabilities	0	0
Total liabilities	323.7	323.7
Total AAM stockholders' deficit	(107.9)	(120.8)
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	(107.9)	(120.8)
Total liabilities and stockholders' deficit	215.8	202.9
AAM Inc. [Member]
Current Assets
Cash and cash equivalents	29.3	10.6	30.2	83.7
Accounts receivable, net	124.9	94.4
Inventories, net	46.0	48.7
Other current assets	48.7	48.8
Total current assets	248.9	202.5
Property, plant and equipment, net	259.3	250.4
Goodwill	0	0
Other assets and deferred charges, condensed	702.8	706.1
Investment in subsidiaries	1,142.3	1,094.6
Total assets	2,353.3	2,253.6
Current Liabilities
Accounts payable	119.5	91.4
Other current liabilities	109.4	124.5
Total current liabilities	228.9	215.9
Intercompany payable (receivable)	(434.2)	(420.6)
Long-term debt	1,487.6	1,387.5
Investment in subsidiaries obligation		0
Other long-term liabilities	855.2	867.9
Total liabilities	2,137.5	2,050.7
Total AAM stockholders' deficit	215.8	202.9
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	215.8	202.9
Total liabilities and stockholders' deficit	2,353.3	2,253.6
Guarantor Subsidiaries [Member]
Current Assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	31.7	25.3
Inventories, net	32.1	31.6
Other current assets	3.8	3.5
Total current assets	67.6	60.4
Property, plant and equipment, net	82.1	84.2
Goodwill	147.8	147.8
Other assets and deferred charges, condensed	42.3	40.0
Investment in subsidiaries	2.5	0
Total assets	342.3	332.4
Current Liabilities
Accounts payable	43.4	37.3
Other current liabilities	4.2	3.8
Total current liabilities	47.6	41.1
Intercompany payable (receivable)	(201.1)	(188.7)
Long-term debt	5.6	5.6
Investment in subsidiaries obligation		7.6
Other long-term liabilities	1.3	1.2
Total liabilities	(146.6)	(133.2)
Total AAM stockholders' deficit	488.9	465.6
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	488.9	465.6
Total liabilities and stockholders' deficit	342.3	332.4
Non-Guarantor Subsidiaries [Member]
Current Assets
Cash and cash equivalents	71.5	51.8	82.6	85.5
Accounts receivable, net	378.7	343.7
Inventories, net	162.5	144.0
Other current assets	75.9	69.7
Total current assets	688.6	609.2
Property, plant and equipment, net	702.1	675.1
Goodwill	8.6	8.6
Other assets and deferred charges, condensed	79.5	81.7
Investment in subsidiaries	0	0
Total assets	1,478.8	1,374.6
Current Liabilities
Accounts payable	291.7	267.4
Other current liabilities	82.9	76.4
Total current liabilities	374.6	343.8
Intercompany payable (receivable)	311.6	285.6
Long-term debt	77.0	61.0
Investment in subsidiaries obligation		0
Other long-term liabilities	59.7	62.8
Total liabilities	822.9	753.2
Total AAM stockholders' deficit	655.9	621.4
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	655.9	621.4
Total liabilities and stockholders' deficit	1,478.8	1,374.6
Elims [Member]
Current Assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Inventories, net	0	0
Other current assets	0	0
Total current assets	0	0
Property, plant and equipment, net	0	0
Goodwill	0	0
Other assets and deferred charges, condensed	0	0
Investment in subsidiaries	(1,360.6)	(1,297.5)
Total assets	(1,360.6)	(1,297.5)
Current Liabilities
Accounts payable	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Intercompany payable (receivable)	0	0
Long-term debt	0	0
Investment in subsidiaries obligation		(7.6)
Other long-term liabilities	0	0
Total liabilities	0	(7.6)
Total AAM stockholders' deficit	(1,360.6)	(1,289.9)
Noncontrolling interest in subsidiaries	0	0
Total stockholders’ deficit	(1,360.6)	(1,289.9)
Total liabilities and stockholders' deficit	$ (1,360.6)	$ (1,297.5)

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.