Securities (Schedule of Book Values and Fair Values of Investment Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Due within one year	$ 0
Due after one year but within five years	28,691
Due after five years but within ten years	59,024
Due after ten years	1,000
Mortgage-backed securities	670,861
Amortized Cost	759,576	$ 812,202
Fair Value
Due within one year	0
Due after one year but within five years	30,393
Due after five years but within ten years	59,260
Due after ten years	880
Mortgage-backed securities	694,299
Total securities	784,832	821,945
Amortized Cost
Due within one year	1,501
Due after one year but within five years	4,856
Due after five years but within ten years	3,587
Due after ten years	48,593
Mortgage-backed securities	36,387
Amortized Cost	94,924	67,932
Fair Value
Due within one year	1,520
Due after one year but within five years	4,982
Due after five years but within ten years	3,669
Due after ten years	48,784
Mortgage-backed securities	37,363
Total securities	$ 96,318	$ 68,333