Investment Securities - Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Within one year	$ 53,380
After one year but within five years	148,049
Amortized Cost	201,429	$ 252,958
Fair value
Within one year	54,005
After one year but within five years	152,522
Total fair value	206,527	$ 256,268
Fair value
Within one year	31,322
After one year but within five years	83,599
After five years but within 10 years	21,868
After 10 years	495
Total fair value	$ 137,284