Common stock (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class A [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	678,523	719,307	742,213
Treasury shares, beginning balance	(34,592)	(17,337)	(12,897)
Shares outstanding, beginning balance	643,931	701,970	729,316
Conversions of Class A common stock to Class B common stock and exercises of replacement stock options			(22,906)
Conversions of Class A common stock to Class B common stock	(12,622)	(40,784)
Conversions of Class A to Class B common stock, Outstanding	(12,622)	(40,784)
Treasury stock acquired	(14,196)	(17,255)	(4,440)
Shares issued, ending balance	665,901	678,523	719,307
Treasury shares, ending balance	(48,788)	(34,592)	(17,337)
Shares outstanding, ending balance	617,113	643,931	701,970
Class B [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	1,469,359,852	1,408,183,852	1,373,558,983
Treasury shares, beginning balance	(119,316,381)	(23,702,319)	(6,138,909)
Shares outstanding, beginning balance	1,350,043,471	1,384,481,533	1,367,420,074
Conversions of Class A common stock to Class B common stock and exercises of replacement stock options			34,624,869
Conversions of Class A common stock to Class B common stock	18,933,000	61,176,000
Conversions of Class A to Class B common stock, Outstanding	18,933,000	61,176,000
Treasury stock acquired	(78,501,968)	(95,614,062)	(17,563,410)
Shares issued, ending balance	1,488,292,852	1,469,359,852	1,408,183,852
Treasury shares, ending balance	(197,818,349)	(119,316,381)	(23,702,319)
Shares outstanding, ending balance	1,290,474,503	1,350,043,471	1,384,481,533