Organization - Additional Information (Detail) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Aug. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 segment
Subsidiary, Sale of Stock [Line Items]
Number of operating segments | segment		1
Public Stock Offering and Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Payments of stock issuance costs	$ 14.2
Total proceeds from stock offering	244.5
Payments of stock issuance costs, portion accrued	0.8
Total proceeds from stock offering, net of offering expenses accrued	$ 243.7
Public Stock Offering
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering (in shares) | shares	9,241,072
Offering price per share (dollars per share) | $ / shares	$ 28
Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering (in shares) | shares	1,205,357