Financial Information for Subsidiary and Guarantor Parent (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
ASSETS
Cash and cash equivalents	$ 380.6				$ 432.3				$ 380.6	$ 432.3	$ 708.8	$ 469.9
Accounts Receivable Net Current	709.1				545.4				709.1	545.4
Total inventories, net	1,384.3				1,024.5				1,384.3	1,024.5
Prepaid expenses and other current assets	95.5				112.9				95.5	112.9
Total Current Assets	2,569.5				2,115.1				2,569.5	2,115.1
Property, plant and equipment, net	2,368.8				1,989.3				2,368.8	1,989.3
Cost in excess of net assets acquired	737.7				206.8				737.7	206.8
Deferred income taxes	0				0				0	0
Investments in subsidiaries and other assets	370.9				182.4				370.9	182.4
Total Assets	6,046.9				4,493.6				6,046.9	4,493.6	4,346.0
LIABILITIES AND EQUITY
Accounts payable	490.7				394.1				490.7	394.1
Accrued liabilities	320.3				249.9				320.3	249.9
Deferred income tax liability current	23.5				5.6				23.5	5.6
Debt Current	27.3				141.4				27.3	141.4
Total Current Liabilities	861.8				791.0				861.8	791.0
Long-term debt	1,482.0				921.9				1,482.0	921.9
Accrued postretirement benefits	488.1				423.8				488.1	423.8
Pension liabilities	508.9				58.3				508.9	58.3
Deferred income taxes	9.8				68.6				9.8	68.6
Other long-term liabilities	124.7				100.6				124.7	100.6
Total Liabilities	3,475.3				2,364.2				3,475.3	2,364.2
Stockholders' Equity	2,571.6				2,129.4				2,571.6	2,129.4	2,089.6	2,029.0
Total Liabilities and Equity	6,046.9				4,493.6				6,046.9	4,493.6
CONSOLIDATED STATEMENTS OF OPERATIONS
Sales									5,183.0	4,047.8	3,054.9
Cost of sales									4,369.8	3,557.5	2,646.5
Selling and administrative expenses									382.1	304.9	315.7
Income (loss) before interest, other income and income taxes									431.1	185.4	92.7
Interest expense, net									92.3	62.7	19.3
Debt extinguishment costs									0	0	(9.2)
Other income including equity in income of unconsolidated subsidiaries									0.6	3.0	0.7
Income before income tax provision (benefit)									339.4	125.7	64.9
Income tax expense									116.3	47.0	26.9
Net income (loss)									223.1	78.7	38.0
Less: Net income (loss) attributable to noncontrolling interests									8.8	8.0	6.3
Net income (loss) attributable to ATI	31.7	62.3	64.0	56.3	15.1	1.0	36.4	18.2	214.3	70.7	31.7
Statement of Cash Flows
Cash flows provided by (used in) operating activities									296.8	27.1	218.5
Cash provided by (used in) investing activities									(624.7)	(216.8)	(453.7)
Cash provided by (used in) financing activities									276.2	(86.8)	474.1
Increase (decrease) in cash and cash equivalents									(51.7)	(276.5)	238.9
Guarantor Parent
ASSETS
Cash and cash equivalents	0.8				1.9				0.8	1.9
Accounts Receivable Net Current	0.1				0.1				0.1	0.1
Total inventories, net	0				0				0	0
Prepaid expenses and other current assets	10.5				48.6				10.5	48.6
Total Current Assets	11.4				50.6				11.4	50.6
Property, plant and equipment, net	3.0				2.8				3.0	2.8
Cost in excess of net assets acquired	0				0				0	0
Deferred income taxes					0					0
Investments in subsidiaries and other assets	5,287.3				4,249.2				5,287.3	4,249.2
Total Assets	5,301.7				4,302.6				5,301.7	4,302.6
LIABILITIES AND EQUITY
Accounts payable	4.1				5.5				4.1	5.5
Accrued liabilities	961.8				1,179.3				961.8	1,179.3
Deferred income tax liability current	23.5				5.6				23.5	5.6
Debt Current	0				117.3				0	117.3
Total Current Liabilities	989.4				1,307.7				989.4	1,307.7
Long-term debt	1,252.5				752.5				1,252.5	752.5
Accrued postretirement benefits	0				0				0	0
Pension liabilities	441.6				12.9				441.6	12.9
Deferred income taxes	9.8				68.6				9.8	68.6
Other long-term liabilities	36.8				31.5				36.8	31.5
Total Liabilities	2,730.1				2,173.2				2,730.1	2,173.2
Stockholders' Equity	2,571.6				2,129.4				2,571.6	2,129.4
Total Liabilities and Equity	5,301.7				4,302.6				5,301.7	4,302.6
CONSOLIDATED STATEMENTS OF OPERATIONS
Sales									0	0	0
Cost of sales									27.4	44.0	68.5
Selling and administrative expenses									168.6	126.2	127.7
Income (loss) before interest, other income and income taxes									(196.0)	(170.2)	(196.2)
Interest expense, net									81.6	52.2	9.5
Debt extinguishment costs											(9.2)
Other income including equity in income of unconsolidated subsidiaries									617.0	348.1	279.8
Income before income tax provision (benefit)									339.4	125.7	64.9
Income tax expense									116.3	47.0	26.9
Net income (loss)									223.1	78.7	38.0
Less: Net income (loss) attributable to noncontrolling interests									8.8	8.0	6.3
Net income (loss) attributable to ATI									214.3	70.7	31.7
Statement of Cash Flows
Cash flows provided by (used in) operating activities									(16.2)	(23.8)	(46.2)
Cash provided by (used in) investing activities									(385.1)	(0.2)	(132.8)
Cash provided by (used in) financing activities									400.2	18.7	182.8
Increase (decrease) in cash and cash equivalents									(1.1)	(5.3)	3.8
Subsidiary
ASSETS
Cash and cash equivalents	129.7				159.1				129.7	159.1
Accounts Receivable Net Current	220.6				233.3				220.6	233.3
Total inventories, net	299.0				232.6				299.0	232.6
Prepaid expenses and other current assets	20.0				19.2				20.0	19.2
Total Current Assets	669.3				644.2				669.3	644.2
Property, plant and equipment, net	614.9				483.5				614.9	483.5
Cost in excess of net assets acquired	112.1				112.2				112.1	112.2
Deferred income taxes					0					0
Investments in subsidiaries and other assets	1,579.0				1,554.2				1,579.0	1,554.2
Total Assets	2,975.3				2,794.1				2,975.3	2,794.1
LIABILITIES AND EQUITY
Accounts payable	222.5				173.3				222.5	173.3
Accrued liabilities	66.7				62.9				66.7	62.9
Deferred income tax liability current	0				0				0	0
Debt Current	0.1				10.4				0.1	10.4
Total Current Liabilities	289.3				246.6				289.3	246.6
Long-term debt	350.7				350.8				350.7	350.8
Accrued postretirement benefits	215.5				236.6				215.5	236.6
Pension liabilities	5.7				6.2				5.7	6.2
Deferred income taxes	0				0				0	0
Other long-term liabilities	17.2				20.0				17.2	20.0
Total Liabilities	878.4				860.2				878.4	860.2
Stockholders' Equity	2,096.9				1,933.9				2,096.9	1,933.9
Total Liabilities and Equity	2,975.3				2,794.1				2,975.3	2,794.1
CONSOLIDATED STATEMENTS OF OPERATIONS
Sales									2,363.4	2,056.5	1,380.3
Cost of sales									2,129.2	1,968.4	1,284.2
Selling and administrative expenses									50.9	28.8	36.5
Income (loss) before interest, other income and income taxes									183.3	59.3	59.6
Interest expense, net									10.4	10.2	9.8
Debt extinguishment costs											0
Other income including equity in income of unconsolidated subsidiaries									4.1	8.5	2.6
Income before income tax provision (benefit)									177.0	57.6	52.4
Income tax expense									68.8	20.0	18.8
Net income (loss)									108.2	37.6	33.6
Less: Net income (loss) attributable to noncontrolling interests									0	0	0
Net income (loss) attributable to ATI									108.2	37.6	33.6
Statement of Cash Flows
Cash flows provided by (used in) operating activities									78.2	(188.9)	62.5
Cash provided by (used in) investing activities									(160.8)	(68.7)	(48.1)
Cash provided by (used in) financing activities									53.2	(55.5)	176.0
Increase (decrease) in cash and cash equivalents									(29.4)	(313.1)	190.4
Non Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	250.1				271.3				250.1	271.3
Accounts Receivable Net Current	488.4				312.0				488.4	312.0
Total inventories, net	1,085.3				791.9				1,085.3	791.9
Prepaid expenses and other current assets	65.0				45.1				65.0	45.1
Total Current Assets	1,888.8				1,420.3				1,888.8	1,420.3
Property, plant and equipment, net	1,750.9				1,503.0				1,750.9	1,503.0
Cost in excess of net assets acquired	625.6				94.6				625.6	94.6
Deferred income taxes					0					0
Investments in subsidiaries and other assets	996.6				1,001.0				996.6	1,001.0
Total Assets	5,261.9				4,018.9				5,261.9	4,018.9
LIABILITIES AND EQUITY
Accounts payable	264.1				215.3				264.1	215.3
Accrued liabilities	736.2				704.8				736.2	704.8
Deferred income tax liability current	0				0				0	0
Debt Current	27.2				13.7				27.2	13.7
Total Current Liabilities	1,027.5				933.8				1,027.5	933.8
Long-term debt	78.8				18.6				78.8	18.6
Accrued postretirement benefits	272.6				187.2				272.6	187.2
Pension liabilities	61.6				39.2				61.6	39.2
Deferred income taxes	0				0				0	0
Other long-term liabilities	70.7				49.1				70.7	49.1
Total Liabilities	1,511.2				1,227.9				1,511.2	1,227.9
Stockholders' Equity	3,750.7				2,791.0				3,750.7	2,791.0
Total Liabilities and Equity	5,261.9				4,018.9				5,261.9	4,018.9
CONSOLIDATED STATEMENTS OF OPERATIONS
Sales									2,819.6	1,991.3	1,674.6
Cost of sales									2,213.2	1,545.1	1,293.8
Selling and administrative expenses									162.6	149.9	151.5
Income (loss) before interest, other income and income taxes									443.8	296.3	229.3
Interest expense, net									0.3	0.3	0
Debt extinguishment costs											0
Other income including equity in income of unconsolidated subsidiaries									2.6	3.8	5.7
Income before income tax provision (benefit)									446.1	299.8	235.0
Income tax expense									155.1	124.0	93.6
Net income (loss)									291.0	175.8	141.4
Less: Net income (loss) attributable to noncontrolling interests									8.8	8.0	6.3
Net income (loss) attributable to ATI									282.2	167.8	135.1
Statement of Cash Flows
Cash flows provided by (used in) operating activities									234.8	271.2	184.3
Cash provided by (used in) investing activities									(74.3)	(123.0)	(334.5)
Cash provided by (used in) financing activities									(181.7)	(106.3)	194.9
Increase (decrease) in cash and cash equivalents									(21.2)	41.9	44.7
Eliminations
ASSETS
Cash and cash equivalents	0				0				0	0
Accounts Receivable Net Current	0				0				0	0
Total inventories, net	0				0				0	0
Prepaid expenses and other current assets	0				0				0	0
Total Current Assets	0				0				0	0
Property, plant and equipment, net	0				0				0	0
Cost in excess of net assets acquired	0				0				0	0
Deferred income taxes					0					0
Investments in subsidiaries and other assets	(7,492.0)				(6,622.0)				(7,492.0)	(6,622.0)
Total Assets	(7,492.0)				(6,622.0)				(7,492.0)	(6,622.0)
LIABILITIES AND EQUITY
Accounts payable	0				0				0	0
Accrued liabilities	(1,444.4)				(1,697.1)				(1,444.4)	(1,697.1)
Deferred income tax liability current	0				0				0	0
Debt Current	0				0				0	0
Total Current Liabilities	(1,444.4)				(1,697.1)				(1,444.4)	(1,697.1)
Long-term debt	(200.0)				(200.0)				(200.0)	(200.0)
Accrued postretirement benefits	0				0				0	0
Pension liabilities	0				0				0	0
Deferred income taxes	0				0				0	0
Other long-term liabilities	0				0				0	0
Total Liabilities	(1,644.4)				(1,897.1)				(1,644.4)	(1,897.1)
Stockholders' Equity	(5,847.6)				(4,724.9)				(5,847.6)	(4,724.9)
Total Liabilities and Equity	(7,492.0)				(6,622.0)				(7,492.0)	(6,622.0)
CONSOLIDATED STATEMENTS OF OPERATIONS
Sales									0	0	0
Cost of sales									0	0	0
Selling and administrative expenses									0	0	0
Income (loss) before interest, other income and income taxes									0	0	0
Interest expense, net									0	0	0
Debt extinguishment costs											0
Other income including equity in income of unconsolidated subsidiaries									(623.1)	(357.4)	(287.4)
Income before income tax provision (benefit)									(623.1)	(357.4)	(287.4)
Income tax expense									(223.9)	(144.0)	(112.4)
Net income (loss)									(399.2)	(213.4)	(175.0)
Less: Net income (loss) attributable to noncontrolling interests									(8.8)	(8.0)	(6.3)
Net income (loss) attributable to ATI									(390.4)	(205.4)	(168.7)
Statement of Cash Flows
Cash flows provided by (used in) operating activities									0	(31.4)	17.9
Cash provided by (used in) investing activities									(4.5)	(24.9)	61.7
Cash provided by (used in) financing activities									4.5	56.3	(79.6)
Increase (decrease) in cash and cash equivalents									$ 0	$ 0	$ 0