Equity - Shareholders' Equity (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Mandatory conversion of 6% convertible preferred stock			4,000,000
Balance December 31	3,577,103,522	3,577,103,522
Common Stock [Member]
Balance January 1	3,577,000,000	3,577,000,000	3,563,000,000
Purchases of treasury stock
Issuances			10,000,000
Mandatory conversion of 6% convertible preferred stock			4,000,000
Balance December 31	3,577,000,000	3,577,000,000	3,577,000,000
Treasury Stock [Member]
Balance January 1	536,000,000	495,000,000	454,000,000
Purchases of treasury stock	62,000,000	58,000,000	47,000,000
Issuances	(48,000,000)	(17,000,000)	(6,000,000)
Mandatory conversion of 6% convertible preferred stock
Balance December 31	550,000,000	536,000,000	495,000,000