Common stock (Detail) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class A [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	651,450	665,901	678,523
Treasury shares, beginning balance	(59,886)	(48,788)	(34,592)
Shares outstanding, beginning balance	591,564	617,113	643,931
Conversions of Class A to Class B common stock	(12,122)	(14,451)	(12,622)
Conversions of Class A to Class B common stock, Outstanding	(12,122)	(14,451)	(12,622)
Treasury stock acquired	(11,667)	(11,098)	(14,196)
Shares issued, ending balance	639,328	651,450	665,901
Treasury shares, ending balance	(71,553)	(59,886)	(48,788)
Shares outstanding, ending balance	567,775	591,564	617,113
Class B [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	1,509,969,352	1,488,292,852	1,469,359,852
Treasury shares, beginning balance	(207,715,276)	(197,818,349)	(119,316,381)
Shares outstanding, beginning balance	1,302,254,076	1,290,474,503	1,350,043,471
Conversions of Class A to Class B common stock	18,183,000	21,676,500	18,933,000
Conversions of Class A to Class B common stock, Outstanding	18,183,000	21,676,500	18,933,000
Treasury stock acquired	(9,875,568)	(9,896,927)	(78,501,968)
Shares issued, ending balance	1,528,152,352	1,509,969,352	1,488,292,852
Treasury shares, ending balance	(217,590,844)	(207,715,276)	(197,818,349)
Shares outstanding, ending balance	1,310,561,508	1,302,254,076	1,290,474,503