Other Expenses - Additional Information (Detail) - USD ($)	3 Months Ended				9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
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 (or the period since the date of the first offering of our class A common stock following December 19, 2012, whichever is shorter) 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	$ 13,813,000	$ 5,412,000			$ 28,535,000	$ 13,219,000
Manager [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Management fees	9,400,000	4,600,000			22,900,000	12,400,000
Incentive fees payable	4,500,000	$ 842,000	$ 0	$ 0	5,700,000	$ 842,000
Accrued management fees payable	9,400,000				9,400,000		$ 5,500,000
Accrued incentive fees payable	$ 4,500,000				$ 4,500,000		817,000
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%
Percentage of pool three fourths vested	50.00%				50.00%
Percentage of remaining pool after vesting					50.00%
Fully vested pool, percentage	27.00%				27.00%
Percentage of pool vesting upon receipt of dividends	33.00%				33.00%
Description of incentive management fee awards to employees vesting schedule					Approximately 50% of the pool is three-fourths vested as of September 30, 2015, with the remainder contingent on continued employment with an affiliate of our Manager and our receipt of distributions from CT Legacy Partners. Of the remaining 50% of the pool, 27% is fully vested as a result of an acceleration event, and 33% vest only upon our receipt of distributions from CT Legacy Partners.
Accrued payables, awards	$ 1,300,000				$ 1,300,000		$ 2,800,000