Other Expenses - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
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	$ 13,243,000	$ 13,701,000	$ 40,557,000	$ 43,161,000
Accrued management and incentive fees payable	13,243,000		13,243,000		$ 12,798,000
CT Legacy Partners [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total incentive compensation payments		354,000		1,112,000
Manager [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Management fees	9,500,000	9,500,000	28,600,000	28,400,000
Total incentive compensation payments	3,700,000	4,200,000	11,900,000	14,800,000
Accrued management and incentive fees payable	$ 13,200,000		$ 13,200,000		$ 12,800,000
Incentive Awards Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Percentage of the dividends paid to common equity holders created employee pool	6.75%		6.75%
Incentive Awards Plan [Member] | CT Legacy Partners [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Recognized expenses for incentive plan		$ 354,000.0		$ 1,100,000