Segment and Geographical Area Information by Operating Segment Table (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Net sales:
Net Sales	$ 355.3	$ 343.2
Segment operating income (loss):
Operating income (loss)	59.5	44.8
Interest expense	(5.6)	(3.7)
Other income, net	0.6	0.3
Income before income taxes	54.5	41.4
Depreciation and amortization:
Depreciation and amortization	9.6	8.7
Capital expenditures:
Capital expenditures	14.8	25.9
Assets:
Assets	1,413.1		$ 1,443.5
Unrealized Gain on Derivatives	15.1	4.0
Fabricated Products
Segment operating income (loss):
Operating income (loss)	70.6	57.9
Depreciation and amortization:
Depreciation and amortization	9.4	8.6
Capital expenditures:
Capital expenditures	14.6	25.8
Assets:
Assets	1,017.3		969.4
Unrealized Gain on Derivatives	15.1	4.0
All Other
Segment operating income (loss):
Operating income (loss)	(11.1)	(13.1)
Depreciation and amortization:
Depreciation and amortization	0.2	0.1
Capital expenditures:
Capital expenditures	0.2	$ 0.1
Assets:
Assets	$ 395.8		$ 474.1