Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Loan portfolio payments held by servicer	$ 28,886	$ 6,294
Accrued interest receivable	33,485	32,871
Derivative assets	743	4,086
Prepaid expenses	711	803
Prepaid taxes	7	16
Total	$ 63,832	$ 44,070