Investment Securities - Expected Maturities of Investment Securities Portfolio (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale, Amortized Cost
Within one year	$ 741,828
One to five years	2,591,483
Five to ten years	592,020
Beyond ten years	1,264,032
Total	5,189,363	$ 5,313,209
Available-for-sale, Fair Value
Within one year	762,452
One to five years	2,691,307
Five to ten years	609,108
Beyond ten years	1,297,158
Total	$ 5,360,025	$ 5,385,091
Available-for-sale, Weighted Average Yield
Within one year	1.82%
One to five years	2.73%
Five to ten years	3.41%
Beyond ten years	3.24%
Total	2.80%