Securities, AFS Debt Securities, Contractual Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Available-for-sale Securities, Debt Maturities, Amortized Cost [Abstract]
Within one year	$ 1,265
From one to five years	49,595
From five to ten years	589,435
After ten years	878,354
Amortized cost	1,518,649	$ 1,318,711
Available-for-sale Securities, Debt Maturities, Estimated Fair Value [Abstract]
Within one year	1,273
From one to five years	50,379
From five to ten years	589,990
After ten years	893,091
Fair value	$ 1,534,733	$ 1,348,698