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Segment Information - Geographic Concentration (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Concentration Risk      
Sales $ 5,594 $ 6,473 $ 6,670
South Africa      
Concentration Risk      
Sales $ 646 $ 597 $ 561
Sales | Geographic concentration | South Africa      
Concentration Risk      
Concentration risk (as a percent) 12.00% 9.00% 8.00%
Accounts Receivable | Geographic concentration | Foreign Country      
Concentration Risk      
Foreign receivables, excluding receivables due from affiliates $ 275 $ 267