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Stock Plans - Additional Information (Detail)
3 Months Ended 6 Months Ended
Mar. 31, 2015
Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expiration period   10 years
Stock options exercisable period after grant date   3 years
Share-based compensation arrangement by share-based payment award, fair value assumptions, average closing price used to calculated expected dividend rate, period   1 year
Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Percentage of target award based on achieving targeted performance conditions   0.00%
Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Percentage of target award based on achieving targeted performance conditions   200.00%
Percentage of target award based on achieving specified performance targets 133.60%  
Performance Stock Unit    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting period (in years) 3 years  
Performance Stock Unit    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award, fair value assumptions, average closing price used to calculated expected dividend rate, period   1 year
Stock beta, daily price data period   3 years