Stockholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended										1 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended
	Jun. 09, 2009	Dec. 31, 2011 Year	Dec. 31, 2010 Year	Dec. 31, 2009 Year	Dec. 31, 2011 Minimum	Dec. 31, 2011 Maximum	Dec. 31, 2011 1.875% Convertible Notes	Dec. 31, 2010 1.875% Convertible Notes	Jun. 20, 2007 1.875% Convertible Notes	Dec. 31, 2011 2.50% Convertible Notes	May 23, 2011 2.50% Convertible Notes	Oct. 27, 2011 Stock Repurchase Program Year	Dec. 31, 2011 Stock Repurchase Program	Aug. 13, 2009 Stock Incentive Plan 2009	Dec. 31, 2011 Stock Incentive Plan 2009	Dec. 31, 2011 Warrant Year	Dec. 31, 2010 Warrant Year	Dec. 31, 2009 Warrant Year	Dec. 31, 2011 Restricted Stock Year	Dec. 31, 2010 Restricted Stock	Dec. 31, 2009 Restricted Stock	Dec. 31, 2011 Restricted Stock Minimum	Dec. 31, 2011 Restricted Stock Maximum
Class of Stock [Line Items]
Repurchase of common stock authorized value												$ 200,000,000
Period of common stock repurchase, years												4
Repurchase of common stock, shares													1,150,000
Repurchase of common stock, value		19,138,000		1,455,000									19,100,000
Expiration of repurchase plan													Oct. 30, 2011
Common stock offered, shares	10,700,000
Common stock offered, price per share	$ 15.00
Net proceeds from offering of common stock	152,800,000			152,798,000
Number of common stock shares authorized under Company's 2009 Equity Incentive Plan														3,000,000
Plan expiration date														2019-08-13
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%
Weighted average contractual term of option outstanding		3.09	2.79	3.88
Weighted average contractual term of option exercisable		3.09	2.78	3.87
Fair value of options vested during the period		300,000	100,000
Weighted average grant date fair value per share of options granted during the period		$ 8.85	$ 7.30	$ 9.91
Cash received from option exercise under all share-based payment arrangements		3,300,000	2,100,000	3,200,000
Tax benefit from share based payment arrangement		4,900,000	1,300,000	3,600,000
Aggregate intrinsic value of options exercised		11,600,000	7,500,000	7,300,000
Aggregate intrinsic value of options outstanding		18,600,000	38,100,000	25,300,000
Aggregate intrinsic value of options exercisable		18,600,000	38,100,000	25,300,000
Weighted average contractual term of awards outstanding and exercisable																5.48	4.97	5.97
Share based compensation awards vesting period																						1 year	5 years
Share based compensation awards granted in period																			1,845,403	340,964	684,478
Share based compensation awards granted in period, fair market value																			38,800,000	4,900,000	8,600,000
Compensation expense related to stock grants																			11,400,000	11,300,000	8,900,000
Compensation cost not yet recognized																			15,600,000
Compensation cost not yet recognized, period for recognition																			4
Restricted common stock, value of shares withheld																			$ 3,200,000	$ 3,000,000	$ 700,000
Common stock reserved for issuance															64,266