Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Common Stock - Summary of Restricted Stock Unit Award Activity (Detail) - Restricted Stock Unit [Member]
12 Months Ended
Dec. 31, 2020
$ / shares
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Number of Shares, Beginning Balance | shares 500
Number of Shares, Released | shares (236)
Number of Shares, Forfeited or expired | shares (33)
Number of Shares, Ending Balance | shares 231
Weighted-Average Grant Date Fair Value, Beginning Balance | $ / shares $ 579.85
Weighted-Average Grant Date Fair Value, Released | $ / shares 579.96
Weighted-Average Grant Date Fair Value, Forfeited or expired | $ / shares 578.00
Weighted-Average Grant Date Fair Value, Ending Balance | $ / shares $ 580.00