Share-Based Payments - Additional Information (Detail) (USD $)	3 Months Ended		6 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]
Stock-based compensation expense	$ 329,000	$ 91,000	$ 753,000	$ 189,000
2007 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	5,079,642		5,079,642
Shares available for future issuance	114,393		114,393		684,124
Options granted during period			3,636
Weighted-average grant date fair value of options	$ 6.88	$ 1.83	$ 6.88	$ 1.84
Intrinsic value of options exercised	352,000	19,000	380,000	188,000
Unrecognized compensation expense related to stock option	2,100,000		2,100,000
Weighted-average period to recognize compensation expense			1 year 9 months 18 days
Unvested restricted stock	63,840		63,840
2007 Stock Incentive Plan [Member] | Performance-Based Stock Option Grants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock option	2,900,000		2,900,000
Stock option granted	355,454	375,636
Stock-based compensation expense	$ 45,000	$ 0	$ 217,000	$ 0