Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income [Abstract]
Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax	$ 3.4	$ (9.0)
Aoci Derivative Financial Instruments	(2.7)	0.1
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(0.1)	(0.1)
Defined Benefit Plan Accumulated Other Comprehensive Income Net Of Tax Effect	(1,030.0)	(932.6)
Accumulated Other Comprehensive Income Loss Attributable to ATI, Total	(1,029.4)	(941.6)
Noncontrolling Interest Items Abstract
Noncontrolling Interest Foreign Currency Translation	23.7	21.8
Accumulated Other Comprehensive Income Attributable To Noncontrolling Interests, Total	$ 23.7	$ 21.8