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24. POST-EMPLOYMENT OBLIGATIONS (Details 7)
 12 Months Ended
Dec. 31, 2020
Pension plans and retirement supplement plans - Plan A [member]  
Disclosure of defined benefit plans [line items]  
Average periods of maturity of the obligations under the benefit plans 11 years 6 months 29 days
Pension plans and retirement supplement plans - Plan B [member]  
Disclosure of defined benefit plans [line items]  
Average periods of maturity of the obligations under the benefit plans 12 years 9 months 22 days
Health plan [member]  
Disclosure of defined benefit plans [line items]  
Average periods of maturity of the obligations under the benefit plans 13 years 9 months 18 days
Dental plan [member]  
Disclosure of defined benefit plans [line items]  
Average periods of maturity of the obligations under the benefit plans 15 years 1 month 6 days
Life insurance plan [member]  
Disclosure of defined benefit plans [line items]  
Average periods of maturity of the obligations under the benefit plans 18 years 7 months 28 days