Share-Based Compensation - Stock Options Activity (Detail) (USD $)
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Outstanding at beginning of period, Number of Shares 1,707,114  
Options granted, Number of Shares 247,600  
Options exercised, Number of Shares (514,466)  
Options canceled or expired, Number of Shares (40,123)  
Outstanding at end of period, Number of Shares 1,400,125 1,707,114
Vested or expected to vest at end of period, Number of Shares 1,400,125  
Exercisable at end of period, Number of Shares 1,182,140  
Outstanding at beginning of period, Weighted-Average Exercise Price $ 1.3802  
Options granted, Weighted-Average Exercise Price $ 3.2600  
Options exercised, Weighted-Average Exercise Price $ 0.6472  
Options canceled or expired, Weighted-Average Exercise Price $ 0.8479  
Outstanding at end of period, Weighted-Average Exercise Price $ 1.9825 $ 1.3802
Vested or expected to vest at end of period, Weighted-Average Exercise Price $ 1.9825  
Exercisable at end of period, Weighted-Average Exercise Price $ 1.7461  
Options granted, Weighted-Average Contractual Life 6 years 2 months 12 days  
Options exercised, Weighted-Average Contractual Life 2 years 3 months 18 days  
Options canceled or expired, Weighted-Average Contractual Life 8 years 9 months 18 days  
Outstanding at end of period, Weighted-Average Contractual Life 5 years 3 months 18 days 4 years 4 months 24 days
Exercisable at end of period, Weighted-Average Contractual Life 4 years 7 months 6 days