Inventories (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials and supplies	$ 148.8		$ 149.6
Work-in-process	855.5		837.9
Finished goods	160.0		161.7
Total inventories at current cost	1,164.3		1,149.2
Adjustment from current cost to LIFO cost basis	89.3		97.3
Inventory valuation reserves	(157.6)		(169.0)
Progress payments	(44.1)		(40.5)
Total inventories, net	1,051.9		$ 1,037.0
Inventory [Line Items]
LIFO benefit (charge)	(8.1)	$ (0.3)
NRV benefit (charge)	8.1	0.3
Net cost of sales impact	$ 0.0	0.0
Inventory Valuation Reserve \| Titanium products
Inventory [Line Items]
Inventory valuation charges		$ 10.0

Inventory, Net Realizable Value Reserve, Period Charge

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Lifo Provision Benefit and Change in Debit LIFO NRV reserve, net

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Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.

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Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods.

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The change in the inventory reserve representing the cumulative difference in cost between the first in, first out and the last in, first out inventory valuation methods, which change has been reflected in the statement of income during the period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.

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Amount of valuation reserve for inventory.

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Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer.

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Amount of advances received from customers under long-term contracts which have been offset against inventories accounts at the balance sheet date.

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Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to costs and expenses.

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