Quarterly report pursuant to Section 13 or 15(d)

Common Stock - Summary of Restricted Stock Unit Award Activity (Detail)

v3.10.0.1
Common Stock - Summary of Restricted Stock Unit Award Activity (Detail) - Restricted Stock Unit [Member]
9 Months Ended
Sep. 30, 2018
$ / shares
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Number of Shares, Beginning Balance | shares 21,066
Number of Shares, Released | shares (5,340)
Number of Shares, Forfeited or expired | shares (570)
Number of Shares, Ending Balance | shares 15,156
Weighted-Average Grant Date Fair Value, Beginning Balance | $ / shares $ 38.87
Weighted-Average Grant Date Fair Value, Released | $ / shares 55.62
Weighted-Average Grant Date Fair Value, Forfeited or expired | $ / shares 97.03
Weighted-Average Grant Date Fair Value, Ending Balance | $ / shares $ 30.78