Segment Information, Financial Information by Reporting Segment Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Net sales:
Net Sales	$ 335.1		$ 337.4
Segment operating income (loss):
Operating income (loss)	32.1		50.0
Interest expense	(8.8)		(9.3)
Other income, net	1.9		1.0
Income before income taxes	25.2		41.7
Depreciation and amortization:
Depreciation and amortization	7.4		7.0
Capital expenditures:
Capital expenditures	15.4		9.3
Income taxes paid:
Income taxes paid	0.7		0.7
Assets:
Assets	1,766.0				1,770.9
Fabricated Products
Net sales:
Net Sales	335.1		337.4
Segment operating income (loss):
Operating income (loss)	35.4	[1],[2]	55.2	[1],[2]
Depreciation and amortization:
Depreciation and amortization	7.2		6.9
Capital expenditures:
Capital expenditures	15.3		8.9
Assets:
Assets	853.7				852.5
Fabricated Products | United States
Income taxes paid:
Income taxes paid	0.1		0.4
Fabricated Products | Canada
Income taxes paid:
Income taxes paid	0.6		0.3
All Other
Segment operating income (loss):
Operating income (loss)	(3.3)	[3]	(5.2)	[3]
Depreciation and amortization:
Depreciation and amortization	0.2		0.1
Capital expenditures:
Capital expenditures	0.1		0.4
Assets:
Assets	$ 912.3	[4]			$ 918.4	[4]

[1] Fabricated Products segment results include non-cash mark-to-market gains (losses) on primary aluminum, natural gas, electricity and foreign currency hedging activities totaling $2.0 and $(0.7) for the quarters ended March 31, 2014 and March 31, 2013, respectively. For further discussion regarding mark-to-market matters, see Note 8.

[2] Operating results in the Fabricated Products segment for the quarter ended March 31, 2014 included a charge of $1.8 as a result of decrementing a prior year, higher cost LIFO layer.

[3] Operating results in All Other include VEBA net periodic pension benefit income of $5.6 for both quarters ended March 31, 2014 and March 31, 2013, respectively.

[4] Assets in All Other represent primarily all of the Company’s cash and cash equivalents, short-term investments, financial derivative assets, net assets of VEBA(s) (see Note 5) and net deferred income tax assets.