Income Per Share - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Debt Instrument [Line Items]
Effect of dilutive stock-based compensation awards	694,000	567,000	651,000
Stock-based compensation awards outstanding	817,000	1,735,000	913,000	1,025,000
Effect of potentially issuable shares	3,957,000		2,688,000
Approximate number of common stock share which can be purchased under warrants	13,200,000		13,200,000
Initial strike price under warrant	32.70		32.70
Effect of potentially issuable shares under warrants	2,106,000		583,000
3.75% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	3.75%		3.75%
Convertible senior notes			2014