Earnings Per Share - Additional Information (Detail) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013 Performance Shares	Dec. 31, 2012 Performance Shares	Dec. 31, 2013 Maximum	Dec. 31, 2013 1.50% Convertible Notes	Mar. 18, 2013 1.50% Convertible Notes	Dec. 31, 2012 1.50% Convertible Notes	Dec. 31, 2013 2.50% Convertible Notes	Dec. 31, 2012 2.50% Convertible Notes	May 23, 2011 2.50% Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares	1.7	0	0	0.1
Debt instrument, interest rate, stated percentage					1.50%	1.50%	1.50%	2.50%	2.50%	2.50%