Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Loan portfolio payments held by servicer	$ 135,516	$ 6,294
Accrued interest receivable	30,962	32,871
Derivative assets	1,424	4,086
Prepaid expenses	700	803
Prepaid taxes	14	16
Total	$ 168,616	$ 44,070