Segment Information, Textuals (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Charge relating to decrement of a prior year, higher cost LIFO layer	$ 1.8
Unrealized gains (losses) on derivatives	2.9	(0.3)
VEBA net periodic pension benefit income	5.6	5.6
Fabricated Products
Segment Reporting Information [Line Items]
Unrealized gains (losses) on derivatives	2.0	(0.7)
United States
Segment Reporting Information [Line Items]
Number of production facilities	11
Canada
Segment Reporting Information [Line Items]
Number of production facilities	1
VEBAs
Segment Reporting Information [Line Items]
VEBA net periodic pension benefit income	$ 5.6	$ 5.6