STOCKHOLDERS' EQUITY: - Treasury Stock (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		9 Months Ended
	Aug. 26, 2024	May 23, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Activity in treasury stock
Balance at the beginning of the period					$ 3,149.0
Balance at the end of the period			$ 2,831.0	$ 3,131.1	$ 2,831.0	$ 3,131.1
Dividends paid as cash dividend (in dollars per share)					$ 1.40	$ 3.00
Parent Company (Grupo Mexico) common shares
Activity in treasury stock
Treasury stock balance at the end of the period (in shares)			99,059,107		99,059,107		111,485,617
Dividends paid as cash dividend (in dollars per share)	$ 0.0056	$ 0.0104
Reduction of shares in treasury stock	4,374,118	8,039,992
Treasury stock retired amount	$ 108.6	$ 199.5
TREASURY STOCK:
Activity in treasury stock
Dividend paid in Common Stock			$ 108.6		$ 308.1
TREASURY STOCK: | Parent Company (Grupo Mexico) common shares
Activity in treasury stock
Balance at the beginning of the period					2,766.7	$ 2,766.9
Dividend paid in Common Stock					(308.1)
Used for corporate purposes					(0.3)	(0.2)
Balance at the end of the period			2,458.3	2,766.7	2,458.3	2,766.7
TREASURY STOCK: | Parent Company (Grupo Mexico)
Activity in treasury stock
Balance at the beginning of the period					382.3	340.7
Other activity, including dividend, interest and foreign currency translation effect			(6.5)	(0.6)	(9.6)	23.7
Balance at the end of the period			$ 372.7	$ 364.4	$ 372.7	$ 364.4