Shareholders' Equity - Common Stock Activity (Detail)								12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Common Stock [Member]	Dec. 31, 2011 Common Stock [Member]	Dec. 31, 2010 Common Stock [Member]	Jan. 01, 2010 Common Stock [Member]	Dec. 31, 2012 Treasury Stock [Member]	Dec. 31, 2011 Treasury Stock [Member]	Dec. 31, 2010 Treasury Stock [Member]
Common stock issued
Balance, beginning of year				371,980,460	371,980,460	371,980,460	371,980,460	99,519,509	74,707,547	39,972,796
Repurchase of shares								13,094,640	27,582,889	37,667,829
Share activity under stock-based employee compensation plans								(2,396,704)	(2,770,927)	(2,933,078)
Balance, end of year				371,980,460	371,980,460	371,980,460	371,980,460	110,217,445	99,519,509	74,707,547
Common stock outstanding, end of year	261,763,015	272,460,951	297,272,913