STOCKHOLDERS' EQUITY: - Treasury Stock (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	150 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Activity in treasury stock
Purchase of shares				$ 2,900.0
Balance at the end of the period	$ 3,041.5	$ 3,032.4	$ 3,032.4	$ 3,041.5
Southern Copper common shares
Activity in treasury stock
Treasury stock balance at the end of the period (in shares)	111,537,217			111,537,217	111,537,217
TREASURY STOCK: | Southern Copper common shares
Activity in treasury stock
Balance at the beginning of the period	$ 2,767.9	2,768.3
Used for corporate purposes		(0.4)	(0.4)
Balance at the end of the period	2,767.9	2,767.9	2,767.9	$ 2,767.9
TREASURY STOCK: | Parent Company (Grupo Mexico) common shares
Activity in treasury stock
Balance at the beginning of the period	281.0	251.3
Other activity, including dividend, interest and foreign currency transaction effect	(7.4)	13.2
Balance at the end of the period	$ 273.6	$ 264.5	$ 264.5	$ 273.6
Treasury stock balance at the end of the period (in shares)	91,987,011			91,987,011	93,082,532