EQUITY - Additional information (Details)
 12 Months Ended
Feb. 27, 2020
PEN (S/)
S/ / shares
Feb. 27, 2019
PEN (S/)
Feb. 28, 2018
PEN (S/)
Feb. 22, 2017
PEN (S/)
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2019
PEN (S/)
S/ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2018
PEN (S/)
S/ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Dec. 31, 2017
PEN (S/)
S/ / shares
shares
Dec. 31, 2019
PEN (S/)
shares
Sep. 25, 2019
PEN (S/)
Dec. 31, 2018
PEN (S/)
shares
Dec. 31, 2017
PEN (S/)
shares
Oct. 25, 2017
USD ($)
Oct. 25, 2017
PEN (S/)
Disclosure of equity [Line Items]                                
Number of shares issued | shares                     94,382,317   94,382,317 94,382,317    
Par value per share | $ / shares         $ 5   $ 5   $ 5              
Purchase of treasury shares | $         $ 31,000,000   $ 29,300,000   $ 21,900,000.00000              
Description of significant restrictions on entity's statutory reserve         required to keep a reserve that equals a percentage of paid-in capital (20, 30 or 50 percent, depending on its activities and the country in which production takes place); this reserve must be constituted with annual transfers of not less than 10 percent of net profits required to keep a reserve that equals a percentage of paid-in capital (20, 30 or 50 percent, depending on its activities and the country in which production takes place); this reserve must be constituted with annual transfers of not less than 10 percent of net profits                    
Statutory reserve                     S/ 6,236,500,000   S/ 5,179,000,000 S/ 4,480,300,000    
Increase (decrease) through transfer to statutory reserve, equity   S/ 1,858,800,000 S/ 2,933,600,000 S/ 2,355,000,000                        
Dividends paid, classified as financing activities         $ 481,215,000 S/ 1,595,229,000 $ 343,292,000 S/ 1,130,427,000 $ 298,114,000 S/ 979,989,000            
Dividends paid, ordinary shares per share | S/ / shares           S/ 20.0000   S/ 14.1726   S/ 12.2865            
Withholding tax rate         5.00% 5.00% 5.00% 5.00% 5.00% 5.00%            
Capital commitments                     S/ 25,732,000,000   S/ 25,063,900,000.00000      
Increase of capital requirement           S/ 4,151,600,000   S/ 4,658,100,000                
Interim dividend payable                       S/ 638,400,000     $ 386,500,000 S/ 1,252,300,000
Date of dividend paid                 November 2017 November 2017            
Non adjusting Event Member [Member]                                
Disclosure of equity [Line Items]                                
Dividends paid, classified as financing activities S/ 2,831,500,000                              
Dividends recognised as distributions to owners per share | S/ / shares S/ 30.00                              
Date on which dividend will be paid May 08, 2020                              
Group [Member]                                
Disclosure of equity [Line Items]                                
Purchase of number of treasury shares | shares         129,807 129,807 133,750 133,750 132,110 132,110