Stock Repurchase Program - Additional Information (Detail) (USD $)	36 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Equity [Abstract]
Stock repurchase program, authorized amount					$ 950,000,000.0
Stock repurchase from inception	$ 846,200,000
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
Executives
Equity, Class of Treasury Stock [Line Items]
Stock surrendered during period (in shares)		0	3,378	9,529