Investment Securities - Expected Maturities of Investment Securities Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Available-for-sale, Amortized Cost
Within one year	$ 360,037
One to five years	2,113,684
Five to ten years	4,728,394
Beyond ten years	2,016,134
Total	9,218,249	$ 7,384,033
Available-for-sale, Fair Value
Within one year	359,809
One to five years	2,063,545
Five to ten years	4,461,469
Beyond ten years	1,865,781
Total	$ 8,750,604	7,382,066
Available-for-sale, Weighted Average Yield
Within one year	1.13%
One to five years	2.37%
Five to ten years	2.07%
Beyond ten years	2.29%
Total	2.15%
Held-to-Maturity, Amortized Cost
Within one year	$ 253
One to five years	4,028
Five to ten years	524,913
Beyond ten years	1,553,048
Total	2,082,242	0
Held-to-Maturity, Fair Value
Within one year	254
One to five years	3,965
Five to ten years	499,835
Beyond ten years	1,451,542
Total	$ 1,955,596	$ 0
Held-to-Maturity, Weighted Average Yield
Within one year	3.85%
One to five years	3.63%
Five to ten years	2.26%
Beyond ten years	2.65%
Total	2.56%