CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Sales	$ 972.4	$ 1,131.5	$ 3,128.2	$ 3,645.5
Costs and expenses:
Cost of sales	919.3	988.8	2,886.9	3,139.6
Selling and administrative expenses	70.6	77.6	210.1	243.3
Income (loss) before interest, other income and income taxes	(17.5)	65.1	31.2	262.6
Interest expense, net	(18.2)	(17.2)	(46.5)	(55.7)
Other income, net	0.4	0.2	1.3	0.6
Income (loss) from continuing operations before income tax provision (benefit)	(35.3)	48.1	(14.0)	207.5
Income tax provision (benefit)	(8.5)	14.8	(4.4)	66.6
Income (loss) from continuing operations	(26.8)	33.3	(9.6)	140.9
Income (loss)from discontinued operations, net of tax	(5.4)	4.0	(4.4)	13.4
Net income (loss)	(32.2)	37.3	(14.0)	154.3
Less: Net income (loss) attributable to noncontrolling interests	1.6	2.0	5.4	6.4
Net income (loss) attributable to ATI	(33.8)	35.3	(19.4)	147.9
Basic income (loss) from continuing operations attributable to ATI per common share (in dollars per share)	$ (0.27)	$ 0.30	$ (0.14)	$ 1.27
Basic income (loss) from discontinued operations attributable to ATI per common share (in dollars per share)	$ (0.05)	$ 0.03	$ (0.04)	$ 0.12
Basic net income (loss) attributable to ATI per common share (in dollars per share)	$ (0.32)	$ 0.33	$ (0.18)	$ 1.39
Diluted income (loss) from continuing operations attributable to ATI per common share (in dollars per share)	$ (0.27)	$ 0.29	$ (0.14)	$ 1.21
Diluted income (loss) from discontinued operations attributable to ATI per common share (in dollars per share)	$ (0.05)	$ 0.03	$ (0.04)	$ 0.11
Diluted net income (loss) attributable to ATI per common share (in dollars per share)	$ (0.32)	$ 0.32	$ (0.18)	$ 1.32
Dividends declared per common share (in dollars per share)	$ 0.18	$ 0.18	$ 0.54	$ 0.54
Income (loss) from continuing operations, net of tax	(28.4)	31.3	(15.0)	134.5
Income (loss) from discontinued operations, net of tax	$ (5.4)	$ 4.0	$ (4.4)	$ 13.4