Common Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class A [Member]
Class of Stock [Line Items]
Shares issued	788,058	820,102	838,019	868,616
Treasury shares	(11,680)	(11,680)	(11,680)	(9,573)
Shares outstanding	776,378	808,422	826,339	859,043
Conversions of Class A common stock to Class B common stock and exercises of replacement stock options issued in a business acquisition	(32,044)	(17,917)	(30,597)
Treasury shares acquired			(2,107)
Class B [Member]
Class of Stock [Line Items]
Shares issued	1,303,323,927	1,253,866,598	1,226,265,250	1,178,775,092
Treasury shares	(1,409,762)	(1,409,762)	(1,409,762)	(1,408,484)
Shares outstanding	1,301,914,165	1,252,456,836	1,224,855,488	1,177,366,608
Conversions of Class A common stock to Class B common stock and exercises of replacement stock options issued in a business acquisition	49,457,329	27,601,348	47,490,158
Treasury shares acquired			(1,278)