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Share-Based Compensation, T-Bucks EPP and Long-Term Incentive Plan (Details)
$ / shares in Units, ZAR in Millions, $ in Millions
12 Months Ended
Dec. 31, 2012
USD ($)
$ / shares
shares
Dec. 31, 2012
ZAR
shares
Mar. 31, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
shares
T-Bucks Employee Participation Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Amount funded to the trust $ 15 ZAR 124    
T-Bucks Employee Participation Plan [Member] | Class A [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares acquired by the Trust (in shares) 548,234 548,234    
Per share fair value on the date of purchase (in dollars per share) | $ / shares $ 25.79      
Shares outstanding (in shares)     548,234 548,234
Long-term Incentive Plan [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Long term incentive plan liability | $     $ 1 $ 1