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Stock Based Compensation - Additional Information (Detail) (USD $)
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3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 0 Months Ended | 6 Months Ended | |||||
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Jun. 30, 2014
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Jun. 30, 2013
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Jun. 30, 2014
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Jun. 30, 2013
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Jun. 30, 2014
Employee Stock-Based Compensation Expense
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Jun. 30, 2013
Employee Stock-Based Compensation Expense
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Jun. 30, 2014
Employee Stock-Based Compensation Expense
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Jun. 30, 2013
Employee Stock-Based Compensation Expense
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May 15, 2014
2004 Equity Incentive Plan
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Jun. 30, 2014
2004 Equity Incentive Plan
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Jun. 30, 2014
2004 Employee Stock Purchase Plan
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||||||||||
| Stock-based compensation expense | $ 1,468,000 | $ 1,272,000 | $ 2,734,000 | $ 2,325,000 | $ 1,500,000 | $ 1,200,000 | $ 2,700,000 | $ 2,200,000 | |||
| Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans | 12,700,000 | 12,700,000 | |||||||||
| Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition | 2 years 8 months 12 days | ||||||||||
| Non-employee stock-based compensation expense | 19,000 | 34,000 | 55,000 | 100,000 | |||||||
| Additional shares authorized for issuance | 6,626,157 | 1,250,000 | 100,000 | ||||||||
| Shares authorized for issuance under the 2014 Equity Incentive Plan | 6,000,000 | ||||||||||
| Remaining shares available for issuance | 4,446,294 | 261,834 | |||||||||
| Total intrinsic value of stock options exercised | 200,000 | 400,000 | |||||||||
| Cash received from stock option exercises | 100,000 | 200,000 | |||||||||
| Plan participants purchased shares | 74,062 | ||||||||||
| Average purchase price under 2004 Employee Stock Purchase Plan | $ 3.91 | ||||||||||
| Cash proceeds | $ 300,000 | ||||||||||