Investment Securities - Schedule Of Amortized Cost And Fair Value By Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Held-to-Maturity, Amortized Cost
Within 1 year	$ 0
After 1 year; within 5 years	0
After 5 years; within 10 years	10,000
After 10 years	0
Subtotal	10,000
Government agency issued MBS and CMO	0
Total	10,000	$ 10,000
Held-to-Maturity, Fair Value
Within 1 year	0
After 1 year; within 5 years	0
After 5 years; within 10 years	9,881
After 10 years	0
Subtotal	9,881
Government agency issued MBS and CMO	0
Securities held to maturity, fair value	9,881	10,001
Available-for-Sale, Amortized Cost
Within 1 year	1,106,238
After 1 year; within 5 years	137,571
After 5 years; within 10 years	3,573
After 10 years	278,705
Subtotal	1,526,087
Government agency issued MBS and CMO	3,767,659
Securities available for sale, amortized cost	5,293,746
Available-for-Sale, Fair Value
Within 1 year	1,108,000
After 1 year; within 5 years	142,491
After 5 years; within 10 years	9,623
After 10 years	313,395
Subtotal	1,573,509
Government agency issued MBS and CMO	3,902,647
Securities available-for-sale	$ 5,476,156	$ 4,445,403