Loans Held for Sale - Composition of Loans Held for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Receivables Held-for-sale [Abstract]
Multi-family loans, at lower of cost or fair value	$ 447,444	$ 482,873
Total commercial loans held for sale	447,444	482,873
Home equity conversion mortgages, at lower of cost or fair value	1,325	1,325
Residential mortgage loans, at fair value	1,388	2,130
Total consumer loans held for sale	2,713	3,455
Loans held for sale	$ 450,157	$ 486,328