Common stock (Detail)	3 Months Ended
	Mar. 31, 2022 shares
Class A [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	665,901
Treasury shares, beginning balance	(48,788)
Shares outstanding, beginning balance	617,113
Conversions of Class A common stock to Class B common stock	(1,148)
Conversions of Class A to Class B common stock, Outstanding	(1,148)
Treasury stock acquired	(2,005)
Shares issued, ending balance	664,753
Treasury shares, ending balance	(50,793)
Shares outstanding, ending balance	613,960
Class B [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	1,488,292,852
Treasury shares, beginning balance	(197,818,349)
Shares outstanding, beginning balance	1,290,474,503
Conversions of Class A common stock to Class B common stock	1,722,000
Conversions of Class A to Class B common stock, Outstanding	1,722,000
Treasury stock acquired	(6,824,671)
Shares issued, ending balance	1,490,014,852
Treasury shares, ending balance	(204,643,020)
Shares outstanding, ending balance	1,285,371,832