Shareholders' Equity - Common Stock Activity (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Treasury stock balance, beginning of year	123,673,969	110,217,445	99,519,509
Repurchase of shares	16,893,455	14,887,701	13,094,640
Share activity under stock-based employee compensation plans	(1,016,353)	(1,431,177)	(2,396,704)
Treasury stock balance, end of year	139,551,071	123,673,969	110,217,445
Common stock outstanding, end of year	232,429,389	248,306,491	261,763,015
Common Stock [Member]
Balance, beginning of year				371,980,460
Balance, end of year	371,980,460	371,980,460	371,980,460	371,980,460