Financial Information for Subsidiary and Guarantor Parent (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
ASSETS [Abstract]
Cash and cash equivalents	$ 210.3	$ 367.8	$ 210.3	$ 367.8	$ 380.6	$ 432.3
Accounts Receivable Net Current	744.3		744.3		709.1
Total inventories, net	1,512.5		1,512.5		1,384.3
Deferred income taxes	0		0
Prepaid expenses and other current assets	60.4		60.4		95.5
Total Current Assets	2,527.5		2,527.5		2,569.5
Property, plant and equipment, net	2,444.0		2,444.0		2,368.8
Cost in excess of net assets acquired	737.7		737.7		737.7
Deferred income taxes	0		0		0
Investments in subsidiaries and other assets	370.8		370.8		370.9
Total Assets	6,080.0		6,080.0		6,046.9
LIABILITIES AND EQUITY [Abstract]
Accounts payable	451.7		451.7		490.7
Accrued liabilities	327.9		327.9		320.3
Deferred income tax liability current	16.6		16.6		23.5
Debt Current	27.3		27.3		27.3
Total Current Liabilities	823.5		823.5		861.8
Long-term debt	1,474.1		1,474.1		1,482.0
Accrued postretirement benefits	473.3		473.3		488.1
Pension liabilities	496.1		496.1		508.9
Deferred income taxes	20.0		20.0		9.8
Other long-term liabilities	117.5		117.5		124.7
Total Liabilities	3,404.5		3,404.5		3,475.3
Stockholders' Equity	2,675.5	2,780.0	2,675.5	2,780.0	2,571.6	2,129.4
Total Liabilities and Equity	6,080.0		6,080.0		6,046.9
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Sales	1,357.4	1,351.6	2,709.9	2,579.0
Cost of sales	1,158.5	1,128.6	2,304.0	2,150.6
Selling and administrative expenses	90.7	99.3	194.1	188.0
Income (loss) before interest, other income and income taxes	108.2	123.7	211.8	240.4
Interest expense, net	18.6	23.7	38.5	46.7
Other income including equity in income of unconsolidated subsidiaries	0.1	0.3	0.5	0.4
Income (loss) before income taxes	89.7	100.3	173.8	194.1
Income tax expense	31.0	34.3	56.8	69.4
Net income (loss)	58.7	66.0	117.0	124.7
Less: Net income (loss) attributable to noncontrolling interests	2.3	2.0	4.4	4.4
Net income (loss) attributable to ATI	56.4	64.0	112.6	120.3
Statement of Cash Flows [Abstract]
Cash flows provided by (used in) operating activities			59.8	(72.0)
Cash provided by (used in) investing activities			(164.8)	(444.3)
Cash provided by (used in) financing activities			(65.3)	451.8
Increase (decrease) in cash and cash equivalents			(170.3)	(64.5)
Statement of Income and Comprehensive Income [Abstract]
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	69.7	73.4	141.8	145.8
Guarantor Parent [Member]
ASSETS [Abstract]
Cash and cash equivalents	4.5		4.5		0.8
Accounts Receivable Net Current	0.1		0.1		0.1
Total inventories, net	0		0		0
Deferred income taxes	0		0
Prepaid expenses and other current assets	2.6		2.6		10.5
Total Current Assets	7.2		7.2		11.4
Property, plant and equipment, net	2.6		2.6		3.0
Cost in excess of net assets acquired	0		0		0
Investments in subsidiaries and other assets	5,497.1		5,497.1		5,287.3
Total Assets	5,506.9		5,506.9		5,301.7
LIABILITIES AND EQUITY [Abstract]
Accounts payable	5.7		5.7		4.1
Accrued liabilities	1,081.7		1,081.7		961.8
Deferred income tax liability current	16.6		16.6		23.5
Debt Current	0		0		0
Total Current Liabilities	1,104.0		1,104.0		989.4
Long-term debt	1,252.5		1,252.5		1,252.5
Accrued postretirement benefits	0		0		0
Pension liabilities	430.1		430.1		441.6
Deferred income taxes	20.0		20.0		9.8
Other long-term liabilities	24.8		24.8		36.8
Total Liabilities	2,831.4		2,831.4		2,730.1
Stockholders' Equity	2,675.5		2,675.5		2,571.6
Total Liabilities and Equity	5,506.9		5,506.9		5,301.7
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Sales	0	0	0	0
Cost of sales	13.4	6.8	26.7	15.4
Selling and administrative expenses	34.9	47.4	78.0	90.3
Income (loss) before interest, other income and income taxes	(48.3)	(54.2)	(104.7)	(105.7)
Interest expense, net	15.6	21.0	32.6	41.5
Other income including equity in income of unconsolidated subsidiaries	153.6	175.5	311.1	341.3
Income (loss) before income taxes	89.7	100.3	173.8	194.1
Income tax expense	31.0	34.3	56.8	69.4
Net income (loss)	58.7	66.0	117.0	124.7
Less: Net income (loss) attributable to noncontrolling interests	2.3	2.0	4.4	4.4
Net income (loss) attributable to ATI	56.4	64.0	112.6	120.3
Statement of Cash Flows [Abstract]
Cash flows provided by (used in) operating activities			(25.9)	39.3
Cash provided by (used in) investing activities			(0.8)	(384.1)
Cash provided by (used in) financing activities			30.4	349.3
Increase (decrease) in cash and cash equivalents			3.7	4.5
Statement of Income and Comprehensive Income [Abstract]
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	69.7	73.4	141.8	145.8
Subsidiary [Member]
ASSETS [Abstract]
Cash and cash equivalents	10.3		10.3		129.7
Accounts Receivable Net Current	257.6		257.6		220.6
Total inventories, net	284.6		284.6		299.0
Deferred income taxes	0		0
Prepaid expenses and other current assets	13.1		13.1		20.0
Total Current Assets	565.6		565.6		669.3
Property, plant and equipment, net	722.6		722.6		614.9
Cost in excess of net assets acquired	112.1		112.1		112.1
Investments in subsidiaries and other assets	210.0		210.0		1,579.0
Total Assets	1,610.3		1,610.3		2,975.3
LIABILITIES AND EQUITY [Abstract]
Accounts payable	213.0		213.0		222.5
Accrued liabilities	337.4		337.4		66.7
Deferred income tax liability current	0		0		0
Debt Current	0.1		0.1		0.1
Total Current Liabilities	550.5		550.5		289.3
Long-term debt	350.6		350.6		350.7
Accrued postretirement benefits	204.3		204.3		215.5
Pension liabilities	5.4		5.4		5.7
Deferred income taxes	0		0		0
Other long-term liabilities	19.2		19.2		17.2
Total Liabilities	1,130.0		1,130.0		878.4
Stockholders' Equity	480.3		480.3		2,096.9
Total Liabilities and Equity	1,610.3		1,610.3		2,975.3
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Sales	573.6	635.9	1,130.6	1,255.0
Cost of sales	526.4	558.3	1,034.9	1,115.7
Selling and administrative expenses	11.9	11.1	22.4	19.6
Income (loss) before interest, other income and income taxes	35.3	66.5	73.3	119.7
Interest expense, net	2.6	2.9	5.2	5.1
Other income including equity in income of unconsolidated subsidiaries	(12.5)	1.0	(10.9)	1.8
Income (loss) before income taxes	20.2	64.6	57.2	116.4
Income tax expense	8.3	24.4	22.3	44.1
Net income (loss)	11.9	40.2	34.9	72.3
Less: Net income (loss) attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to ATI	11.9	40.2	34.9	72.3
Statement of Cash Flows [Abstract]
Cash flows provided by (used in) operating activities			2.6	(75.2)
Cash provided by (used in) investing activities			(127.7)	(48.0)
Cash provided by (used in) financing activities			5.7	90.3
Increase (decrease) in cash and cash equivalents			(119.4)	(32.9)
Statement of Income and Comprehensive Income [Abstract]
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	11.6	39.4	34.3	70.7
Non Guarantor Subsidiaries [Member]
ASSETS [Abstract]
Cash and cash equivalents	195.5		195.5		250.1
Accounts Receivable Net Current	486.6		486.6		488.4
Total inventories, net	1,227.9		1,227.9		1,085.3
Deferred income taxes	0		0
Prepaid expenses and other current assets	44.7		44.7		65.0
Total Current Assets	1,954.7		1,954.7		1,888.8
Property, plant and equipment, net	1,718.8		1,718.8		1,750.9
Cost in excess of net assets acquired	625.6		625.6		625.6
Investments in subsidiaries and other assets	762.9		762.9		996.6
Total Assets	5,062.0		5,062.0		5,261.9
LIABILITIES AND EQUITY [Abstract]
Accounts payable	233.0		233.0		264.1
Accrued liabilities	625.2		625.2		736.2
Deferred income tax liability current	0		0		0
Debt Current	27.2		27.2		27.2
Total Current Liabilities	885.4		885.4		1,027.5
Long-term debt	71.0		71.0		78.8
Accrued postretirement benefits	269.0		269.0		272.6
Pension liabilities	60.6		60.6		61.6
Deferred income taxes	0		0		0
Other long-term liabilities	73.5		73.5		70.7
Total Liabilities	1,359.5		1,359.5		1,511.2
Stockholders' Equity	3,702.5		3,702.5		3,750.7
Total Liabilities and Equity	5,062.0		5,062.0		5,261.9
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Sales	783.8	715.7	1,579.3	1,324.0
Cost of sales	618.7	563.5	1,242.4	1,019.5
Selling and administrative expenses	43.9	40.8	93.7	78.1
Income (loss) before interest, other income and income taxes	121.2	111.4	243.2	226.4
Interest expense, net	0.4	(0.2)	0.7	0.1
Other income including equity in income of unconsolidated subsidiaries	15.0	(0.4)	16.5	0.1
Income (loss) before income taxes	135.8	111.2	259.0	226.4
Income tax expense	48.3	41.4	89.1	81.5
Net income (loss)	87.5	69.8	169.9	144.9
Less: Net income (loss) attributable to noncontrolling interests	2.3	2.0	4.4	4.4
Net income (loss) attributable to ATI	85.2	67.8	165.5	140.5
Statement of Cash Flows [Abstract]
Cash flows provided by (used in) operating activities			83.1	(25.7)
Cash provided by (used in) investing activities			(36.3)	(12.2)
Cash provided by (used in) financing activities			(101.4)	1.8
Increase (decrease) in cash and cash equivalents			(54.6)	(36.1)
Statement of Income and Comprehensive Income [Abstract]
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	72.3	69.3	161.9	156.1
Eliminations [Member]
ASSETS [Abstract]
Cash and cash equivalents	0		0		0
Accounts Receivable Net Current	0		0		0
Total inventories, net	0		0		0
Deferred income taxes	0		0
Prepaid expenses and other current assets	0		0		0
Total Current Assets	0		0		0
Property, plant and equipment, net	0		0		0
Cost in excess of net assets acquired	0		0		0
Investments in subsidiaries and other assets	(6,099.2)		(6,099.2)		(7,492.0)
Total Assets	(6,099.2)		(6,099.2)		(7,492.0)
LIABILITIES AND EQUITY [Abstract]
Accounts payable	0		0		0
Accrued liabilities	(1,716.4)		(1,716.4)		(1,444.4)
Deferred income tax liability current	0		0		0
Debt Current	0		0		0
Total Current Liabilities	(1,716.4)		(1,716.4)		(1,444.4)
Long-term debt	(200.0)		(200.0)		(200.0)
Accrued postretirement benefits	0		0		0
Pension liabilities	0		0		0
Deferred income taxes	0		0		0
Other long-term liabilities	0		0		0
Total Liabilities	(1,916.4)		(1,916.4)		(1,644.4)
Stockholders' Equity	(4,182.8)		(4,182.8)		(5,847.6)
Total Liabilities and Equity	(6,099.2)		(6,099.2)		(7,492.0)
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Sales	0	0	0	0
Cost of sales	0	0	0	0
Selling and administrative expenses	0	0	0	0
Income (loss) before interest, other income and income taxes	0	0	0	0
Interest expense, net	0	0	0	0
Other income including equity in income of unconsolidated subsidiaries	(156.0)	(175.8)	(316.2)	(342.8)
Income (loss) before income taxes	(156.0)	(175.8)	(316.2)	(342.8)
Income tax expense	(56.6)	(65.8)	(111.4)	(125.6)
Net income (loss)	(99.4)	(110.0)	(204.8)	(217.2)
Less: Net income (loss) attributable to noncontrolling interests	(2.3)	(2.0)	(4.4)	(4.4)
Net income (loss) attributable to ATI	(97.1)	(108.0)	(200.4)	(212.8)
Statement of Cash Flows [Abstract]
Cash flows provided by (used in) operating activities			0	(10.4)
Cash provided by (used in) investing activities			0	0
Cash provided by (used in) financing activities			0	10.4
Increase (decrease) in cash and cash equivalents			0	0
Statement of Income and Comprehensive Income [Abstract]
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ (83.9)	$ (108.7)	$ (196.2)	$ (226.8)