Stockholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued in conjunction with the vesting and release of restricted stock units			136,372
Common stock issued due to exercise of stock options			222,174
Common stock issued in connection with employee stock purchase plan			39,651
Employee stock purchase plan, net proceeds			$ 4,500,000
Repurchase of common stock, shares			68,368
Repurchase of common stock	2,000,000		1,956,000	991,000
Amount available under the share repurchase program	50,000,000		50,000,000
Shares repurchase under the share repurchase program	0		0
Share-based compensation expense recognized	1,300,000	1,400,000	4,800,000	5,400,000
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	900,000	800,000	3,300,000	3,100,000
Total unrecognized compensation expense related to non-vested stock options	6,700,000		6,700,000
Expected weighted-average period of recognition for unrecognized compensation expense	2 years 4 months 0 days
Weighted-average grant date fair value of stock options granted			$ 10.95	$ 9.19
Stock options granted			542,020	529,134
Restricted stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	400,000	600,000	1,500,000	2,300,000
Expected weighted-average period of recognition for unrecognized compensation expense	2 years 8 months 18 days
Total unrecognized compensation expense related to non-vested restricted stock	$ 1,700,000		$ 1,700,000
Weighted-average grant date fair value of restricted stock granted			$ 25.34	$ 23.53
Restricted stock granted			116,319	73,994