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Employees - Schedule of Sensitivity of Pension Liabilities to Changes in the Weighted Key Assumptions (Detail)
12 Months Ended
Dec. 31, 2018
Discount Rate [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in assumption Increase by 0.5%
Change in liabilities (7.00%)
Discount Rate [Member] | United Kingdom [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities (8.00%)
Discount Rate [Member] | Netherlands [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities (9.00%)
Inflation Rate [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in assumption Increase by 0.5%
Change in liabilities 6.00%
Inflation Rate [Member] | United Kingdom [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities 7.00%
Inflation Rate [Member] | Netherlands [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities 9.00%
Life expectancy [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in assumption Increase by 1 year
Change in liabilities 4.00%
Life expectancy [Member] | United Kingdom [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities 4.00%
Life expectancy [Member] | Netherlands [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities 4.00%
Long-Term Medical Cost Inflation [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in assumption Increase by 1.0%
Change in liabilities 2.00%
Long-Term Medical Cost Inflation [Member] | United Kingdom [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities 0.00%
Long-Term Medical Cost Inflation [Member] | Netherlands [Member]  
Disclosure of sensitivity analysis for actuarial assumptions [line items]  
Change in liabilities 0.00%