Supplemental Guarantor Condensed Consolidating Financial Statements Condensed Consolidating Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Ownership in Subsidiary, Percentage	100.00%								100.00%
Net sales
External									$ 3,903.1	$ 3,696.0	$ 3,207.3
Intercompany									0.0	0.0	0.0
Total net sales	$ 958.4	$ 971.6	$ 1,004.0	$ 969.1	$ 939.5	$ 950.8	$ 946.9	$ 858.8	3,903.1	3,696.0	3,207.3
Cost of goods sold									3,267.7	3,173.2	2,728.6
Gross Profit	$ 159.8	$ 158.3	$ 164.5	$ 152.8	$ 111.2	$ 140.7	$ 149.0	$ 121.9	635.4	522.8	478.7
Selling, general and administrative expenses									277.3	255.2	238.4
Operating income (loss)									358.1	267.6	240.3
Non-operating income (expense), net									(85.4)	(90.9)	(154.0)
Income (loss) before income taxes									272.7	176.7	86.3
Income tax expense (benefit)									37.1	33.7	(8.2)
Earnings (loss) from equity in subsidiaries									0.0	0.0	0.0
Net income (loss) before royalties									235.6	143.0	94.5
Royalties									0.0	0.0	0.0
Net income after royalties									235.6	143.0	94.5
Other comprehensive income (loss)									(59.6)	(80.7)	48.4
Comprehensive income									176.0	62.3	142.9
Holdings [Member]
Net sales
External									0.0	0.0	0.0
Intercompany									0.0	0.0	0.0
Total net sales									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Gross Profit									0.0	0.0	0.0
Selling, general and administrative expenses									0.0	0.0	0.0
Operating income (loss)									0.0	0.0	0.0
Non-operating income (expense), net									0.0	0.0	0.0
Income (loss) before income taxes									0.0	0.0	0.0
Income tax expense (benefit)									0.0	0.0	0.0
Earnings (loss) from equity in subsidiaries									235.6	143.0	94.5
Net income (loss) before royalties									235.6	143.0	94.5
Royalties									0.0	0.0	0.0
Net income after royalties									235.6	143.0	94.5
Other comprehensive income (loss)									(59.6)	(80.7)	48.4
Comprehensive income									176.0	62.3	142.9
AAM Inc. [Member]
Net sales
External									1,149.0	1,099.5	773.6
Intercompany									9.4	13.1	15.3
Total net sales									1,158.4	1,112.6	788.9
Cost of goods sold									1,114.5	1,112.4	769.4
Gross Profit									43.9	0.2	19.5
Selling, general and administrative expenses									210.6	194.0	182.4
Operating income (loss)									(166.7)	(193.8)	(162.9)
Non-operating income (expense), net									(99.3)	(103.0)	(155.1)
Income (loss) before income taxes									(266.0)	(296.8)	(318.0)
Income tax expense (benefit)									21.6	(11.8)	(24.9)
Earnings (loss) from equity in subsidiaries									262.3	204.0	167.0
Net income (loss) before royalties									(25.3)	(81.0)	(126.1)
Royalties									260.9	224.0	220.6
Net income after royalties									235.6	143.0	94.5
Other comprehensive income (loss)									(59.6)	(80.7)	48.4
Comprehensive income									176.0	62.3	142.9
Guarantor Subsidiaries of Certain Notes [Member]
Net sales
External									210.3	225.1	226.0
Intercompany									258.3	246.9	226.1
Total net sales									468.6	472.0	452.1
Cost of goods sold									385.2	396.1	389.0
Gross Profit									83.4	75.9	63.1
Selling, general and administrative expenses									0.1	0.2	0.0
Operating income (loss)									83.3	75.7	63.0
Non-operating income (expense), net									10.1	9.0	10.7
Income (loss) before income taxes									93.4	84.7	73.7
Income tax expense (benefit)									5.5	0.9	0.9
Earnings (loss) from equity in subsidiaries									(20.8)	(23.3)	(21.7)
Net income (loss) before royalties									67.1	60.5	51.1
Royalties									0.0	0.0	0.0
Net income after royalties									67.1	60.5	51.1
Other comprehensive income (loss)									(63.6)	(23.5)	(7.2)
Comprehensive income									3.5	37.0	43.9
Non-Guarantor Subsidiaries [Member]
Net sales
External									2,543.8	2,371.4	2,207.7
Intercompany									19.0	21.6	14.0
Total net sales									2,562.8	2,393.0	2,221.7
Cost of goods sold									2,054.7	1,946.3	1,825.6
Gross Profit									508.1	446.7	396.1
Selling, general and administrative expenses									66.6	61.0	55.9
Operating income (loss)									441.5	385.7	340.2
Non-operating income (expense), net									3.8	3.1	(9.6)
Income (loss) before income taxes									445.3	388.8	330.6
Income tax expense (benefit)									10.0	44.6	15.8
Earnings (loss) from equity in subsidiaries									0.0	0.0	0.0
Net income (loss) before royalties									435.3	344.2	314.8
Royalties									(260.9)	(224.0)	(220.6)
Net income after royalties									174.4	120.2	94.2
Other comprehensive income (loss)									(68.4)	(34.8)	(10.8)
Comprehensive income									106.0	85.4	83.4
Consolidation, Eliminations [Member]
Net sales
External									0.0	0.0	0.0
Intercompany									(286.7)	(281.6)	(255.4)
Total net sales									(286.7)	(281.6)	(255.4)
Cost of goods sold									(286.7)	(281.6)	(255.4)
Gross Profit									0.0	0.0	0.0
Selling, general and administrative expenses									0.0	0.0	0.0
Operating income (loss)									0.0	0.0	0.0
Non-operating income (expense), net									0.0	0.0	0.0
Income (loss) before income taxes									0.0	0.0	0.0
Income tax expense (benefit)									0.0	0.0	0.0
Earnings (loss) from equity in subsidiaries									(477.1)	(323.7)	(239.8)
Net income (loss) before royalties									(477.1)	(323.7)	(239.8)
Royalties									0.0	0.0	0.0
Net income after royalties									(477.1)	(323.7)	(239.8)
Other comprehensive income (loss)									191.6	139.0	(30.4)
Comprehensive income									$ (285.5)	$ (184.7)	$ (270.2)