Other Expenses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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	$ 54,841	$ 55,959	$ 42,886
Accrued management and incentive fees payable	14,284	12,798
CT Legacy Partners [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total incentive compensation payments		1,094	2,177
Manager [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Management fees	38,600	38,000	32,200
Total incentive compensation payments	16,200	18,000	10,700
Accrued management and incentive fees payable	$ 14,300	12,800
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%
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		$ 1,100	$ 2,200
Incentive Awards Plan [Member] | Manager [Member] | CT Legacy Partners [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total incentive compensation payments	$ 2,800