Restructuring Costs (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) employee	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) employee $ / shares
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 64.3	$ 0.0	$ 67.5
Restructuring costs net of tax			$ 41.6		$ 41.2
Restructuring costs, per share (in dollars per share) | $ / shares			$ 0.39		$ 0.39
Asset Impairment Charges		$ 54.5			$ 55.1
Revision of estimates			$ (0.2)	(1.0)	4.2
Severance and termination benefit costs					8.2
Restructuring reserve	$ 8.0	8.0	8.0		2.0
Restructuring and other charges			89.7	0.0	67.5
Inventory Valuation Reserve [Member] | Non-PQ grade titanium sponge [Member]
Restructuring Cost and Reserve [Line Items]
Lower of cost or market charges		(25.4)
Inventory Valuation Reserve [Member] | Industrial titanium products [Member]
Restructuring Cost and Reserve [Line Items]
Lower of cost or market charges			$ (24.5)	$ (23.2)	(20.5)
Facility Idling Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		3.5
Restructuring costs net of tax		2.2
High Performance Materials & Components and Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Severance and termination benefit costs		$ 6.3
Number of employees affected by restructuring | employee		100
High Performance Materials & Components [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges					8.0
Severance and termination benefit costs					$ 1.1
Number of employees affected by restructuring | employee					75
High Performance Materials & Components [Member] | Benefit Termination [Member]
Restructuring Cost and Reserve [Line Items]
Severance and termination benefit costs					$ 1.1
Midland, Pennsylvania Facility [Member] | Flat Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges	24.2
Grain-Oriented Electrical Steel (GOES) Operations in Western Pennsylvania [Member] | Flat Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges	$ 30.3
Albany, Oregon Standard-grade Titanium Sponge Facility [Member] | High Performance Materials & Components [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges					38.1
Revision of estimates					3.5
New Castle, Indiana Stainless Finishing Facility [Member] | Flat Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges					6.3
Revision of estimates					0.3
Wallingford, Connecticut Stainless Finishing Facility [Member] | Flat Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges					2.7
Revision of estimates					0.4
Severance and termination benefit costs					$ 1.0
Number of employees affected by restructuring | employee					65
Wallingford, Connecticut Stainless Finishing Facility [Member] | Flat Rolled Products [Member] | Benefit Termination [Member]
Restructuring Cost and Reserve [Line Items]
Severance and termination benefit costs					$ 5.0