Stock Repurchase Program - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Repurchase Programs [Line Items]
Stock repurchase program, authorized amount		950.0
Stock repurchase from inception	846.2
Stock repurchased during period (in shares)	27,945,611
Strike prices and taxes due on exercised stock options and vested restricted stock (in shares)	2,651,238
Acquired shares from repurchase program	30,596,849
Treasury shares cancelled and retired, shares		30,497,699
Treasury shares cancelled and retired, reduction in common stock		51.1
Treasury shares cancelled and retired, reduction in retained earnings		885.1
Executives
Stock Repurchase Programs [Line Items]
Stock surrendered during period (in shares)	9,529	179,221	42,762