Other Expenses - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Management fee - percent of outstanding equity balance			1.50%
Incentive fee computation-percent of the product per agreement			20.00%
Incentive fee computation-percent of outstanding Equity per annum			7.00%
Management fees description			our Manager earns a base management fee in an amount equal to 1.50% per annum multiplied by our outstanding equity balance, as defined in the Management Agreement. In addition, our Manager is entitled to an incentive fee in an amount equal to the product of (i) 20% and (ii) the excess of (a) our Core Earnings (as defined in our Management Agreement) for the previous 12-month period over (b) an amount equal to 7.00% per annum multiplied by our outstanding Equity, provided that our Core Earnings over the prior three-year period is greater than zero. Core Earnings, as defined in our Management Agreement, is generally equal to our GAAP net income (loss), including realized gains and losses not otherwise recognized in current period GAAP net income (loss), and excluding (i) non-cash equity compensation expense, (ii) depreciation and amortization, (iii) unrealized gains (losses), (iv) certain non-cash items, and (v) incentive management fees.
Management fees	$ 21,545	$ 20,496	$ 40,752	$ 39,773
Manager [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Management fees	15,600	14,800	31,100	29,200
Total incentive compensation payments	6,000	5,700	9,600	$ 10,500
Accrued management and incentive fees payable	$ 21,500		$ 21,500		$ 19,200
Manager [Member] | Class A Common Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock Issued During Period, Value, Issued for Services		$ 19,300
Stock Issued During Period, Shares, Issued for Services		840,696