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Defined Benefit Plans - Summary of Principal Actuarial Assumptions (Detail)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Supplemental pension plan [member]    
Disclosure of defined benefit plans [line items]    
Expected return on plan assets   3.90%
Discount rate - beginning of year 3.90% 4.00%
Discount rate - end of year   3.90%
Rate of salary escalation   2.00%
Average remaining service period of active employees expected to receive benefits   7 years 1 month 6 days
Greece [member] | Defined Benefit Pension Plans [member]    
Disclosure of defined benefit plans [line items]    
Discount rate - beginning of year 1.60% 2.00%
Discount rate - end of year 1.70% 1.60%
Rate of salary escalation 2.80% 2.80%
Turkey [member] | Defined Benefit Pension Plans [member]    
Disclosure of defined benefit plans [line items]    
Discount rate - beginning of year 10.50% 10.50%
Discount rate - end of year 11.00% 10.50%
Rate of salary escalation 6.50% 6.00%
Canada [member] | Defined Benefit Pension Plans [member]    
Disclosure of defined benefit plans [line items]    
Expected return on plan assets 3.90% 3.90%
Discount rate - beginning of year 3.90% 4.00%
Discount rate - end of year 3.40% 3.90%
Rate of salary escalation 2.00% 2.00%
Average remaining service period of active employees expected to receive benefits 8 years 2 months 12 days 7 years 1 month 6 days
Canada [member] | Supplemental pension plan [member]    
Disclosure of defined benefit plans [line items]    
Expected return on plan assets 3.90%  
Discount rate - beginning of year 3.90%  
Discount rate - end of year 3.40% 3.90%
Rate of salary escalation 2.00%  
Average remaining service period of active employees expected to receive benefits 8 years 2 months 12 days