Acquisitions (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Jan. 01, 2016 location	Dec. 31, 2015 USD ($)
Acquisitions
Net sales	$ 2,162.7	$ 2,614.4
Allocation of the total purchase price of the acquisitions to the fair value of the assets acquired and liabilities assumed
Goodwill	1,824.6			$ 1,724.8
Tubular Steel
Acquisitions
Number of locations of the acquiree entity | location			7
Net sales	29.8
Allocation of the total purchase price of the acquisitions to the fair value of the assets acquired and liabilities assumed
Cash	0.2
Accounts receivable	10.6
Inventories	57.6
Property, plant and equipment	43.4
Goodwill	96.0
Intangible assets subject to amortization	61.7
Intangible assets not subject to amortization	27.3
Other current and long-term assets	0.1
Total assets acquired	296.9
Other current and long-term liabilities	5.8
Net assets acquired	291.1
Summary purchase price allocation information for all acquisitions
Tax deductible goodwill amount	$ 96.0