Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction
Investment in money market or mutual funds managed by affiliates of a related party	$ 47,282	$ 76,658	$ 47,282	$ 76,658	$ 53,199	$ 164,144
Management fee – related party	6,719	10,058	25,292	28,816
Affiliate of the Manager
Related Party Transaction
Investment in money market or mutual funds managed by affiliates of a related party	46,900		$ 46,900		$ 47,400
Manager
Related Party Transaction
Management fee (as a percentage)			1.50%
Management fee – related party	6,700	$ 10,100	$ 25,292	$ 28,816
Management fees accrued but not paid	9,000		$ 9,000
Termination fee multiplier			3
Termination fees assessment period			24 months
Accounting for Premiums and discounts Associated with Purchase of Non-Agency RMBS | Manager
Related Party Transaction
Cumulative one-time adjustment	$ 2,300