XML 720 R240.htm IDEA: XBRL DOCUMENT v3.20.4
Post-retirement benefits - Summary of main assumptions rate for valuations of plans (Detail)
Dec. 31, 2020
Dec. 31, 2019
Disclosure of defined benefit plans [Line Items]    
Assumption for the consumer price index 2.10% 2.00%
Canada    
Disclosure of defined benefit plans [Line Items]    
Discount rate 2.50% 3.10%
Inflation 1.60% 1.60%
Rate of increase in pensions 0.10% 0.10%
Rate of increase in salaries 2.80% 2.80%
UK    
Disclosure of defined benefit plans [Line Items]    
Discount rate 1.20% 2.00%
Inflation 2.90% 2.90%
Rate of increase in pensions 2.50% 2.50%
Rate of increase in salaries 3.60% 3.50%
United States of America    
Disclosure of defined benefit plans [Line Items]    
Discount rate 2.20% 3.10%
Inflation 2.10% 2.00%
Rate of increase in pensions 0.00% 0.00%
Rate of increase in salaries 3.60% 3.50%
Switzerland    
Disclosure of defined benefit plans [Line Items]    
Discount rate 0.10% 0.20%
Inflation 0.90% 1.10%
Rate of increase in pensions 0.50% 0.20%
Rate of increase in salaries 1.90% 2.10%