Intangible Assets, net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Intangible assets subject to amortization:
Intangible assets subject to amortization, Gross Carrying Amount	$ 740.2		$ 674.7
Intangible assets subject to amortization, Accumulated Amortization	(314.7)		(299.6)
Intangible assets
Intangible assets, Gross Carrying Amount	1,519.7		1,425.0
Amortization expense for intangible assets	13.6	$ 14.3
Changes in intangible assets due to foreign currency translation gains	4.2
Summary of estimated aggregate amortization expense for the remaining nine months of 2016 and each of the succeeding five years
2016	39.6
2017	49.0
2018	44.7
2019	44.6
2020	44.6
2021	40.6
Tubular Steel
Intangible assets
Intangible assets recorded in connection with our 2016 acquisition	89.0
Trade names
Intangible assets not subject to amortization:
Intangible assets not subject to amortization, Gross Carrying Amount	779.5		750.3
Trade names | Tubular Steel
Intangible assets
Intangible assets recorded in connection with our 2016 acquisition	$ 27.3
Covenants not to compete
Intangible assets subject to amortization:
Weighted average amortizable life in years	4 years 4 months 24 days
Intangible assets subject to amortization, Gross Carrying Amount	$ 1.4		1.3
Intangible assets subject to amortization, Accumulated Amortization	$ (1.1)		(1.0)
Customer lists/relationships
Intangible assets subject to amortization:
Weighted average amortizable life in years	14 years 10 months 24 days
Intangible assets subject to amortization, Gross Carrying Amount	$ 724.3		659.0
Intangible assets subject to amortization, Accumulated Amortization	$ (300.1)		(285.7)
Software - internal use
Intangible assets subject to amortization:
Weighted average amortizable life in years	10 years
Intangible assets subject to amortization, Gross Carrying Amount	$ 8.1		8.1
Intangible assets subject to amortization, Accumulated Amortization	$ (8.1)		(7.9)
Other
Intangible assets subject to amortization:
Weighted average amortizable life in years	5 years 3 months 18 days
Intangible assets subject to amortization, Gross Carrying Amount	$ 6.4		6.3
Intangible assets subject to amortization, Accumulated Amortization	$ (5.4)		$ (5.0)