Common stock (Detail) - shares	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Class A [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	639,328	651,450	665,901
Treasury shares, beginning balance	(71,553)	(59,886)	(48,788)
Shares outstanding, beginning balance	567,775	591,564	617,113
Conversions of Class A to Class B common stock	(15,426)	(12,122)	(14,451)
Conversions of Class A to Class B common stock, Outstanding	(15,426)	(12,122)	(14,451)
Treasury stock acquired	(4,787)	(11,667)	(11,098)
Shares issued, ending balance	623,902	639,328	651,450
Treasury shares, ending balance	(76,340)	(71,553)	(59,886)
Shares outstanding, ending balance	547,562	567,775	591,564
Class B [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	1,528,152,352	1,509,969,352	1,488,292,852
Treasury shares, beginning balance	(217,590,844)	(207,715,276)	(197,818,349)
Shares outstanding, beginning balance	1,310,561,508	1,302,254,076	1,290,474,503
Conversions of Class A to Class B common stock	23,139,000	18,183,000	21,676,500
Conversions of Class A to Class B common stock, Outstanding	23,139,000	18,183,000	21,676,500
Treasury stock acquired		(9,875,568)	(9,896,927)
Treasury stock issued	2,291,631
Shares issued, ending balance	1,551,291,352	1,528,152,352	1,509,969,352
Treasury shares, ending balance	(215,299,213)	(217,590,844)	(207,715,276)
Shares outstanding, ending balance	1,335,992,139	1,310,561,508	1,302,254,076