Stockholders' Equity - Shares Issued under Share Based Compensation (Detail)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock options exercised 171 8
Total 281 120
RSUs vested    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
RSUs vested 58 76
Shares purchased pursuant to ESPP    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares purchased pursuant to ESPP 52 36