Supplemental Guarantor Condensed Consolidating Financial Statements Supplemental Guarantor Condensed Consolidating Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net sales
External	$ 1,025.4	$ 1,004.0	$ 1,994.6	$ 1,973.1
Intercompany	0.0	0.0	0.0	0.0
Total net sales	1,025.4	1,004.0	1,994.6	1,973.1
Cost of goods sold	834.0	839.5	1,629.2	1,655.8
Gross profit	191.4	164.5	365.4	317.3
Selling, general and administrative expenses	79.9	70.6	155.5	139.1
Operating Income (loss)	111.5	93.9	209.9	178.2
Non-operating income (expense), net	(19.8)	(22.4)	(41.8)	(44.3)
Income (loss) before income taxes	91.7	71.5	168.1	133.9
Income tax expense	20.7	12.9	36.0	22.1
Earnings (loss) from equity in subsidiaries	0.0	0.0	0.0	0.0
Net income (loss) before royalties	71.0	58.6	132.1	111.8
Royalties	0.0	0.0	0.0	0.0
Net income after royalties	71.0	58.6	132.1	111.8
Other comprehensive income (loss), net of tax	(4.4)	2.7	18.2	(25.4)
Comprehensive income	66.6	61.3	150.3	86.4
Holdings [Member]
Net sales
External	0.0	0.0	0.0	0.0
Intercompany	0.0	0.0	0.0	0.0
Total net sales	0.0	0.0	0.0	0.0
Cost of goods sold	0.0	0.0	0.0	0.0
Gross profit	0.0	0.0	0.0	0.0
Selling, general and administrative expenses	0.0	0.0	0.0	0.0
Operating Income (loss)	0.0	0.0	0.0	0.0
Non-operating income (expense), net	0.0	0.0	0.0	0.0
Income (loss) before income taxes	0.0	0.0	0.0	0.0
Income tax expense	0.0	0.0	0.0	0.0
Earnings (loss) from equity in subsidiaries	71.0	58.6	132.1	111.8
Net income (loss) before royalties	71.0	58.6	132.1	111.8
Royalties	0.0	0.0	0.0	0.0
Net income after royalties	71.0	58.6	132.1	111.8
Other comprehensive income (loss), net of tax	(4.4)	2.7	18.2	(25.4)
Comprehensive income	66.6	61.3	150.3	86.4
AAM Inc. [Member]
Net sales
External	308.4	298.7	591.6	573.6
Intercompany	2.8	2.4	4.4	5.5
Total net sales	311.2	301.1	596.0	579.1
Cost of goods sold	291.8	292.7	568.1	563.6
Gross profit	19.4	8.4	27.9	15.5
Selling, general and administrative expenses	70.2	60.1	137.7	119.6
Operating Income (loss)	(50.8)	(51.7)	(109.8)	(104.1)
Non-operating income (expense), net	(23.5)	(25.3)	(47.8)	(50.7)
Income (loss) before income taxes	(74.3)	(77.0)	(157.6)	(154.8)
Income tax expense	13.2	7.5	21.0	12.0
Earnings (loss) from equity in subsidiaries	86.3	81.6	179.2	156.5
Net income (loss) before royalties	(1.2)	(2.9)	0.6	(10.3)
Royalties	72.2	61.5	131.5	122.1
Net income after royalties	71.0	58.6	132.1	111.8
Other comprehensive income (loss), net of tax	(4.4)	2.7	18.2	(25.4)
Comprehensive income	66.6	61.3	150.3	86.4
Guarantor Subsidiaries [Member]
Net sales
External	56.7	56.7	111.5	113.9
Intercompany	63.3	65.9	123.0	130.3
Total net sales	120.0	122.6	234.5	244.2
Cost of goods sold	96.9	99.7	189.4	200.3
Gross profit	23.1	22.9	45.1	43.9
Selling, general and administrative expenses	0.0	0.0	0.0	0.0
Operating Income (loss)	23.1	22.9	45.1	43.9
Non-operating income (expense), net	2.5	2.8	5.5	5.1
Income (loss) before income taxes	25.6	25.7	50.6	49.0
Income tax expense	0.1	0.1	0.2	(0.3)
Earnings (loss) from equity in subsidiaries	(11.3)	(3.4)	(20.9)	(9.4)
Net income (loss) before royalties	14.2	22.2	29.5	39.9
Royalties	0.0	0.0	0.0	0.0
Net income after royalties	14.2	22.2	29.5	39.9
Other comprehensive income (loss), net of tax	6.5	(0.2)	22.2	(27.2)
Comprehensive income	20.7	22.0	51.7	12.7
Non-Guarantor Subsidiaries [Member]
Net sales
External	660.3	648.6	1,291.5	1,285.6
Intercompany	4.1	5.3	7.8	9.9
Total net sales	664.4	653.9	1,299.3	1,295.5
Cost of goods sold	515.5	520.7	1,006.9	1,037.6
Gross profit	148.9	133.2	292.4	257.9
Selling, general and administrative expenses	9.7	10.5	17.8	19.5
Operating Income (loss)	139.2	122.7	274.6	238.4
Non-operating income (expense), net	1.2	0.1	0.5	1.3
Income (loss) before income taxes	140.4	122.8	275.1	239.7
Income tax expense	7.4	5.3	14.8	10.4
Earnings (loss) from equity in subsidiaries	0.0	0.0	0.0	0.0
Net income (loss) before royalties	133.0	117.5	260.3	229.3
Royalties	(72.2)	(61.5)	(131.5)	(122.1)
Net income after royalties	60.8	56.0	128.8	107.2
Other comprehensive income (loss), net of tax	0.4	(0.3)	20.2	(29.0)
Comprehensive income	61.2	55.7	149.0	78.2
Consolidation, Eliminations [Member]
Net sales
External	0.0	0.0	0.0	0.0
Intercompany	(70.2)	(73.6)	(135.2)	(145.7)
Total net sales	(70.2)	(73.6)	(135.2)	(145.7)
Cost of goods sold	(70.2)	(73.6)	(135.2)	(145.7)
Gross profit	0.0	0.0	0.0	0.0
Selling, general and administrative expenses	0.0	0.0	0.0	0.0
Operating Income (loss)	0.0	0.0	0.0	0.0
Non-operating income (expense), net	0.0	0.0	0.0	0.0
Income (loss) before income taxes	0.0	0.0	0.0	0.0
Income tax expense	0.0	0.0	0.0	0.0
Earnings (loss) from equity in subsidiaries	(146.0)	(136.8)	(290.4)	(258.9)
Net income (loss) before royalties	(146.0)	(136.8)	(290.4)	(258.9)
Royalties	0.0	0.0	0.0	0.0
Net income after royalties	(146.0)	(136.8)	(290.4)	(258.9)
Other comprehensive income (loss), net of tax	(2.5)	(2.2)	(60.6)	81.6
Comprehensive income	$ (148.5)	$ (139.0)	$ (351.0)	$ (177.3)