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Stock-Based Compensation - Restricted Stock Units and Restricted Stock Activity (Detail) - 2007 Plan [Member] - Restricted Stock Units (RSUs) [Member]
3 Months Ended
Mar. 31, 2022
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Unvested Shares, Beginning Balance | shares 940,834
Granted, Shares | shares 26,316
Vested, Shares | shares (43,334)
Forfeited, Shares | shares (5,000)
Unvested Shares, Ending Balance | shares 918,816
Unvested, Weighted-Average Grant-Date Fair Value, Beginning Balance | $ / shares $ 2.77
Granted, Weighted-Average Grant-Date Fair Value | $ / shares 1.90
Vested, Weighted-Average Grant-Date Fair Value | $ / shares 2.63
Forfeited, Weighted-Average Grant-Date Fair Value | $ / shares 2.85
Unvested, Weighted-Average Grant-Date Fair Value, Ending Balance | $ / shares $ 2.75