Stockholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended							1 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2012 1.875% Convertible Notes	Dec. 31, 2011 1.875% Convertible Notes	Jun. 20, 2007 1.875% Convertible Notes	Mar. 31, 2012 2.50% Convertible Notes	Dec. 31, 2011 2.50% Convertible Notes	May 23, 2011 2.50% Convertible Notes	Aug. 13, 2009 Stock Incentive Plan 2009	Mar. 31, 2012 Stock Incentive Plan 2009	Oct. 27, 2011 Stock Repurchase Program Year	Mar. 31, 2012 Stock Repurchase Program	Mar. 31, 2012 Restricted Stock Year	Mar. 31, 2011 Restricted Stock	Mar. 31, 2012 Minimum	Mar. 31, 2012 Maximum
Class of Stock [Line Items]
Number of common stock shares authorized under Company's 2009 Equity Incentive Plan								3,000,000
Plan expiration date								2019-08-13
Repurchase of common stock authorized value										$ 200,000,000
Period of common stock repurchase, years										3
Repurchase of common stock, shares											2,051,654
Repurchase of common stock, value	35,662,000										35,700,000
Stock repurchase, remaining available amount											145,200,000
Options grant, expected life	7 years													5 years	10 years
Debt instrument, interest rate, stated percentage		1.875%	1.875%	1.875%	2.50%	2.50%	2.50%
Compensation expense related to stock grants												2,600,000	2,300,000
Compensation cost not yet recognized												13,600,000
Compensation cost not yet recognized, period for recognition												4
Restricted common stock, value of shares withheld												$ 200,000	$ 1,800,000
Common stock reserved for issuance									26,433