Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Debt securities held-to-maturity	$ 92,580	$ 96,167
Loan portfolio payments held by servicer	60,978	6,133
Accrued interest receivable	60,907	56,679
Derivative assets	25,009	9,916
Collateral deposited under derivative agreements	2,310
Prepaid taxes	750	6
Prepaid expenses	43	647
Other	478	965
Total	$ 243,055	$ 170,513