Common stock (Detail)	9 Months Ended
	Sep. 30, 2024 shares
Class A [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	639,328
Treasury shares, beginning balance	(71,553)
Shares outstanding, beginning balance	567,775
Conversions of Class A to Class B common stock	(10,778)
Conversions of Class A to Class B common stock, Outstanding	(10,778)
Treasury stock acquired	(4,787)
Shares issued, ending balance	628,550
Treasury shares, ending balance	(76,340)
Shares outstanding, ending balance	552,210
Class B [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	1,528,152,352
Treasury shares, beginning balance	(217,590,844)
Shares outstanding, beginning balance	1,310,561,508
Conversions of Class A to Class B common stock	16,167,000
Conversions of Class A to Class B common stock, Outstanding	16,167,000
Treasury stock issued	1,368,508
Shares issued, ending balance	1,544,319,352
Treasury shares, ending balance	(216,222,336)
Shares outstanding, ending balance	1,328,097,016