Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2013	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Tax Credit Carryforward [Line Items]
Annual distribution of net taxable income for U.S. federal income tax not to apply to our earnings that we distribute (percent)				90.00%
Net taxable income subject to distribution (percent)				100.00%
Excise tax rate				4.00%
Income tax provision (benefit)		$ 70	$ 20	$ 346	$ 192
Deferred tax assets		0		0		$ 0
Deferred tax liabilities		0		$ 0		0
Common stock, shares issued	25,875,000			10,001,429	10,842,295
Net operating losses carried forward						$ 159,000
NOLs expiration date						Dec. 31, 2029
Open tax year				2017 2018 2019 2020
Internal Revenue Service [Member]
Tax Credit Carryforward [Line Items]
Net operating losses limit per annum		$ 2,000		$ 2,000
Net operating losses limitations				the availability of our NOLs is generally limited to $2.0 million per annum