Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Restricted Stock Activity (Detail)

v3.19.1
Stockholders' Equity - Restricted Stock Activity (Detail) - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares, Restricted stock granted 490,000 1,128,750
Restricted Stock [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares, Unvested balance 11,874,034 10,094,095
Number of shares, Restricted stock granted 1,721,802 1,325,396
Number of shares, Restricted stock vested (213,334) (213,333)
Number of shares, Restricted stock units granted 490,000 1,128,750
Number of shares, Restricted stock units forfeited (474,478) (15,000)
Number of shares Restricted stock units vested (752,042) (445,874)
Number of shares, Unvested balance 12,645,982 11,874,034
Weighted average grant price, Unvested balance $ 2.63 $ 2.49
Weighted average grant price, Restricted stock granted 3.81 2.70
Weighted average grant price, Restricted stock vested 2.76 2.75
Weighted average grant price, Restricted stock units granted 3.64 4.17
Weighted average grant price, Restricted stock units forfeited 3.94 2.98
Weighted average grant price, Restricted stock units vested 3.56 3.50
Weighted average grant price, Unvested balance $ 2.72 $ 2.63