Acquisitions and Divestitures (Assets Acquired and Liability Assumed - Alcan Cable China) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 03, 2012
Business Acquisition [Line Items]
Goodwill	$ 26.1	$ 184.6	$ 187.6
CHINA [Member] | Alcan Cable [Member]
Business Acquisition [Line Items]
Cash				8.4
Accounts receivable				8.5	[1]
Inventories				20.5
Property, plant and equipment				58.8	[2]
Intangible assets				0
Goodwill				0
Other current and noncurrent assets				0.2
Total Assets				96.4
Current liabilities				18.6
Other liabilities				20.1	[2]
Total liabilities				38.7
Adjustments to property, plant and equipment and other liabilities				$ 20

[1] Accounts receivable is gross contractual value. As of the acquisition date, the fair value of accounts receivable approximated carrying value.

[2] Final purchase price accounting includes immaterial adjustments to Property, plant, and equipment and Other liabilities of approximately $20 million.