Stock-Based Compensation - Additional Information (Detail) - USD ($)
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1 Months Ended |
3 Months Ended |
9 Months Ended |
12 Months Ended |
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Jan. 01, 2016 |
May 05, 2015 |
Mar. 31, 2016 |
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
Dec. 31, 2014 |
Dec. 31, 2015 |
Apr. 16, 2015 |
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Number of shares granted during period |
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371,577
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| Employee payroll deductions included in additional paid in capital |
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$ 579,000
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$ 579,000
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$ 669,000
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| Compensation expense |
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$ 767,000
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$ 1,972,000
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$ 2,669,000
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$ 3,126,000
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| Employee Stock Purchase Plan [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Common stock reserved for issuance |
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300,000
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| Percentage of shares outstanding |
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1.00%
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| Increase in number of shares available for issuance |
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150,000
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| Future issuance of employee stock purchase plan |
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428,481
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428,481
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| Employee payroll deductions included in additional paid in capital |
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$ 148,000
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$ 148,000
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| Compensation expense |
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$ 19,000
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$ 64,000
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| Equity Award Plans [Member] | 2006 Plan [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Number of shares granted during period |
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0
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| Equity Award Plans [Member] | 2015 Plan [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Number of shares granted during period |
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527,812
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| Common stock reserved for issuance |
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1,819,100
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| Reserved share, percentage of outstanding shares |
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6.00%
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| Shares authorized and reserved for issuance |
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1,200,000
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| Additional number of shares reserved for issuance |
687,312
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| Stock Option Awards [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Expected dividend rate |
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0.00%
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| Contractual term, options |
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10 years
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| Contractual term, vesting |
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4 years
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| Closing price of common stock |
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$ 38.15
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$ 38.15
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| Unrecognized stock-based compensation expense relating to unvested employee stock options |
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$ 3,900,000
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5,200,000
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$ 3,900,000
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5,200,000
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| Unrecognized stock-based compensation expense, weighted average period |
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2 years 7 months 6 days
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| Weighted average fair value of options granted |
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$ 9.62
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$ 7.26
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| Compensation expense |
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$ 569,000
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1,075,000
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$ 1,934,000
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1,671,000
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| Stock Option Awards [Member] | Minimum [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Risk-free interest rate |
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0.50%
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| Expected average option life |
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3 months 18 days
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| Expected volatility |
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75.90%
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| Expected forfeiture rate |
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12.40%
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| Stock Option Awards [Member] | Maximum [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Risk-free interest rate |
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2.10%
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| Expected average option life |
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10 years
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| Expected volatility |
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98.70%
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| Expected forfeiture rate |
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14.80%
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| Restricted Stock Units [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Contractual term, vesting |
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48 months
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| Unrecognized stock-based compensation expense, weighted average period |
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2 years 10 months 24 days
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| Restricted shares issued |
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360,508
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158,000
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| Restricted stock granted, weighted average fair value |
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$ 10.00
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$ 6.75
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| Restricted stock requisite service period |
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4 years
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4 years
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| Description of vesting of restricted stock units |
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whereby the awards vest in a series of 48 successive equal monthly installments with the first monthly installment vesting on the grant date and the future installments vesting on the first day of each calendar month thereafter.
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| Unrecognized compensation cost |
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1,800,000
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$ 1,800,000
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| Compensation expense |
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$ 179,000
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$ 897,000
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$ 671,000
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$ 1,455,000
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| Restricted Stock Units [Member] | After Six Month Of Grant [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Restricted stock award vested percentage |
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50.00%
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| Restricted Stock Units [Member] | After One Year Of Grant [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Contractual term, vesting |
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1 year
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| Restricted stock award vested percentage |
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12.50%
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| Restricted Stock Units [Member] | After Thirty Six Months Of Grant [Member] |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Contractual term, vesting |
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36 months
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