Supplemental Guarantor Condensed Consolidating Statements of Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net sales
External	$ 946.9	$ 799.6	$ 1,805.7	$ 1,555.2
Intercompany	0	0	0	0
Total net sales	946.9	799.6	1,805.7	1,555.2
Cost of goods sold	797.9	677.4	1,534.8	1,328.7
Gross profit	149.0	122.2	270.9	226.5
Selling, general and administrative expenses	61.5	60.5	118.6	120.1
Operating income (loss)	(87.5)	(61.7)	(152.3)	(106.4)
Non-operating income (expense), net	(24.0)	(30.5)	(48.2)	(70.3)
Income (loss) before income taxes	63.5	31.2	104.1	36.1
Income tax expense	11.3	5.4	18.3	3.0
Earnings (loss) from equity in subsidiaries	0	0	0	0
Net income (loss) before royalties and dividends	52.2	25.8	85.8	33.1
Royalties and dividends	0	0	0	0
Net income after royalties and dividends	52.2	25.8	85.8	33.1
Other comprehensive income (loss)	4.7	(22.1)	18.5	(17.8)
Comprehensive income	56.9	3.7	104.3	15.3
Holdings [Member]
Net sales
External	0	0	0	0
Intercompany	0	0	0	0
Total net sales	0	0	0	0
Cost of goods sold	0	0	0	0
Gross profit	0	0	0	0
Selling, general and administrative expenses	0	0	0	0
Operating income (loss)	0	0	0	0
Non-operating income (expense), net	0	0	0	0
Income (loss) before income taxes	0	0	0	0
Income tax expense	0	0	0	0
Earnings (loss) from equity in subsidiaries	52.2	25.8	85.8	33.1
Net income (loss) before royalties and dividends	52.2	25.8	85.8	33.1
Royalties and dividends	0	0	0	0
Net income after royalties and dividends	52.2	25.8	85.8	33.1
Other comprehensive income (loss)	4.7	(22.1)	18.5	(17.8)
Comprehensive income	56.9	3.7	104.3	15.3
AAM Inc. [Member]
Net sales
External	298.0	211.3	525.9	411.6
Intercompany	3.0	4.6	5.8	8.0
Total net sales	301.0	215.9	531.7	419.6
Cost of goods sold	288.5	197.7	520.4	396.2
Gross profit	12.5	18.2	11.3	23.4
Selling, general and administrative expenses	52.0	52.3	100.6	101.2
Operating income (loss)	39.5	34.1	89.3	77.8
Non-operating income (expense), net	(25.9)	(29.3)	(51.7)	(70.8)
Income (loss) before income taxes	(65.4)	(63.4)	(141.0)	(148.6)
Income tax expense	6.0	(12.3)	6.5	(13.9)
Earnings (loss) from equity in subsidiaries	68.0	24.5	122.5	64.9
Net income (loss) before royalties and dividends	(3.4)	(26.6)	(25.0)	(69.8)
Royalties and dividends	55.6	52.4	110.8	102.9
Net income after royalties and dividends	52.2	25.8	85.8	33.1
Other comprehensive income (loss)	4.7	(22.1)	18.5	(17.8)
Comprehensive income	56.9	3.7	104.3	15.3
Guarantor Subsidiaries [Member]
Net sales
External	59.0	58.8	117.0	112.7
Intercompany	62.5	56.3	120.7	113.9
Total net sales	121.5	115.1	237.7	226.6
Cost of goods sold	102.9	98.9	202.5	196.1
Gross profit	18.6	16.2	35.2	30.5
Selling, general and administrative expenses	0.1	0	0.1	0
Operating income (loss)	(18.5)	(16.2)	(35.1)	(30.5)
Non-operating income (expense), net	2.4	2.7	5.1	5.4
Income (loss) before income taxes	20.9	18.9	40.2	35.9
Income tax expense	0.1	0	0.2	0
Earnings (loss) from equity in subsidiaries	(7.0)	(9.7)	(16.2)	(12.9)
Net income (loss) before royalties and dividends	13.8	9.2	23.8	23.0
Royalties and dividends	0	0	0	0
Net income after royalties and dividends	13.8	9.2	23.8	23.0
Other comprehensive income (loss)	3.3	(21.3)	11.2	(13.6)
Comprehensive income	17.1	(12.1)	35.0	9.4
Non-Guarantor Subsidiaries [Member]
Net sales
External	589.9	529.5	1,162.8	1,030.9
Intercompany	6.1	2.4	12.0	7.3
Total net sales	596.0	531.9	1,174.8	1,038.2
Cost of goods sold	478.1	444.1	950.4	865.6
Gross profit	117.9	87.8	224.4	172.6
Selling, general and administrative expenses	9.4	8.2	17.9	18.9
Operating income (loss)	(108.5)	(79.6)	(206.5)	(153.7)
Non-operating income (expense), net	(0.5)	(3.9)	(1.6)	(4.9)
Income (loss) before income taxes	108.0	75.7	204.9	148.8
Income tax expense	5.2	17.7	11.6	16.9
Earnings (loss) from equity in subsidiaries	0	0	0	0
Net income (loss) before royalties and dividends	102.8	58.0	193.3	131.9
Royalties and dividends	(55.6)	(52.4)	(110.8)	(102.9)
Net income after royalties and dividends	47.2	5.6	82.5	29.0
Other comprehensive income (loss)	2.6	(24.4)	11.5	(16.1)
Comprehensive income	49.8	(18.8)	94.0	12.9
Elims [Member]
Net sales
External	0	0	0	0
Intercompany	(71.6)	(63.3)	(138.5)	(129.2)
Total net sales	(71.6)	(63.3)	(138.5)	(129.2)
Cost of goods sold	(71.6)	(63.3)	(138.5)	(129.2)
Gross profit	0	0	0	0
Selling, general and administrative expenses	0	0	0	0
Operating income (loss)	0	0	0	0
Non-operating income (expense), net	0	0	0	0
Income (loss) before income taxes	0	0	0	0
Income tax expense		0	0	0
Earnings (loss) from equity in subsidiaries	(113.2)	(40.6)	(192.1)	(85.1)
Net income (loss) before royalties and dividends	(113.2)	(40.6)	(192.1)	(85.1)
Royalties and dividends	0	0	0	0
Net income after royalties and dividends	(113.2)	(40.6)	(192.1)	(85.1)
Other comprehensive income (loss)	(10.6)	67.8	(41.2)	47.5
Comprehensive income	$ (123.8)	$ 27.2	$ (233.3)	$ (37.6)