Number of new stock issued during the period.

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Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Common Stock - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	May 31, 2020	Sep. 30, 2020	Sep. 30, 2019
Class of Stock [Line Items]
Net proceeds after offering costs from sale of common stock		$ 206,626	$ 300,000
Public Underwritten Offering
Class of Stock [Line Items]
Common stock issued and sold in public underwritten offering (in shares)	41,325,000
Net proceeds after offering costs from sale of common stock	$ 196,500