Interest-Bearing Deposits - Components of Interest-Bearing Deposits (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
Interest-bearing demand deposits	$ 250,353	$ 254,981
Savings deposits	4,305,391	3,896,536
Time deposits	562,964	835,851
Total interest-bearing deposits	$ 5,118,708	$ 4,987,368