XML 92 R80.htm IDEA: XBRL DOCUMENT v3.10.0.1
Financial Instruments and Risk Management - General (Details)
$ / shares in Units, shares in Millions, $ in Millions
6 Months Ended
Jun. 30, 2018
USD ($)
approach
$ / shares
shares
Dec. 31, 2017
USD ($)
Financial Instruments and Risk Management    
Aggregate fair value of derivative instruments with credit-risk-related contingent features that were in a net liability position $ 9.0 $ 27.0
Collateral amount posted for derivative instruments with credit-risk-related contingent features that were in a net liability position $ 0.0 $ 0.0
Commodity contracts    
Financial Instruments and Risk Management    
Number of methods through which entity manages commodity price risk in connection with market price fluctuations of aluminum ingot | approach 2  
Notional amount of derivatives $ 784.0  
Net gain expected to be recognized in the consolidated statement of earnings during the next 12 months 27.0  
Gain (loss) on derivatives included in AOCI, net of tax 28.0  
Commodity contracts | Derivatives Designated As Hedging Instruments | Cash Flow Hedging    
Financial Instruments and Risk Management    
Notional amount of derivatives $ 707.0  
Commodity contracts | Maximum    
Financial Instruments and Risk Management    
Period within which derivative will expire 2 years  
Interest rate swap and option contracts    
Financial Instruments and Risk Management    
Notional amount of derivatives $ 1,100.0  
Period within which derivative will expire 2 years  
Currency Exchange Rate Risk    
Financial Instruments and Risk Management    
Notional amount of derivatives $ 2,150.0  
Period within which derivative will expire 2 years  
Net after-tax gain (loss) included in AOCI $ (1.0)  
Cross-currency swap    
Financial Instruments and Risk Management    
Period within which derivative will expire 3 years  
Gain (loss) on derivatives included in AOCI, net of tax $ (28.0)  
Amount of hedge contract 1,000.0  
Fair value of swaps $ (92.0)  
Equity contracts    
Financial Instruments and Risk Management    
Change in company's stock price (in dollars per share) | $ / shares $ 1  
Combined notional value (in shares) | shares 2.6  
Fair value of swaps $ 4.0