XML 130 R83.htm IDEA: XBRL DOCUMENT v3.8.0.1
Asset Retirement Obligations - Summary of Present Value of Estimated Future Net Cash Outflows (Detail)
Dec. 31, 2017
Dec. 31, 2016
Greece [member] | Bottom of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.00% 2.00%
Discount rate 1.50% 1.50%
Greece [member] | Top of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.20% 2.40%
Discount rate 3.00% 3.00%
Brazil [member]    
Disclosure of asset retirement obligations [line items]    
Discount rate 1.80% 0.80%
Brazil [member] | Bottom of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.00% 2.00%
Brazil [member] | Top of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.20% 2.40%
Turkey [member] | Bottom of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.00% 2.00%
Discount rate 2.30% 2.30%
Turkey [member] | Top of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.20% 2.40%
Discount rate 2.50% 2.50%
Romania [member]    
Disclosure of asset retirement obligations [line items]    
Discount rate 2.70% 2.70%
Romania [member] | Bottom of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.00% 2.00%
Romania [member] | Top of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.20% 2.40%
Canada [member] | Bottom of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.00%  
Discount rate 2.30%  
Canada [member] | Top of range [member]    
Disclosure of asset retirement obligations [line items]    
Inflation rate 2.20%  
Discount rate 2.50%