Other Expenses - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
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				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 net income (loss) prepared in accordance with GAAP, excluding (i) certain non-cash items, (ii) the net income (loss) related to our legacy portfolio, and (iii) incentive management fees.
Management fees	$ 20,496		$ 20,984	$ 39,773	$ 40,774
Manager [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Management fees	14,800		13,300	29,200	26,400
Total incentive compensation payments	5,700		$ 7,700	10,500	$ 14,400
Accrued management and incentive fees payable	20,500			$ 20,500		$ 20,200
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	840,696