Stockholder's Equity - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of outstanding common stock			$ 100,000,000		$ 25,000,000
Repurchase program term			August 1, 2013
Aggregate number of shares repurchased to date			1,338,055
Aggregate price of shares repurchased to date	13,600,000		13,600,000
Outstanding warrants expire on varying dates			June 2015
Weighted average grant date fair value of stock options granted			$ 8.71	$ 7.57
Share-based compensation expense	2,924,000	3,082,000	5,671,000	6,097,000
Shares of common stock, fully vested, issuable upon conversion or exercise of rights granted	16,300,000		16,300,000
Antidilutive options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	1,600,000	1,300,000	3,000,000	2,600,000
Unrecognized compensation expense	12,200,000		12,200,000
Weighted average period to recognized compensation expense			2 years 4 months 28 days
Restricted stock awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	1,100,000	1,300,000	2,000,000	2,500,000
Unrecognized compensation expense	6,700,000		6,700,000
Weighted average period to recognized compensation expense			2 years 8 months 1 day
Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of common stock purchase price			85.00%
Purchase Plan offering period			6 months
Maximum number of common stock shares available for purchase per participant			50,000
Maximum number of common stock value available for purchase per participant			25,000
Purchase Plan, termination date			2019
Common stock authorized for issuance under purchase plan	5,000,000		5,000,000
Number of shares issued			420,046
401(k) Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock as 401(k) Plan match			50,970	26,154
Value of common stock as 401(k) Plan match, contributions of our employees			$ 446,000	$ 333,500