Investment Securities - Debt Maturities (Details) - Debt Securities - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost
Due within one year	$ 1,013,044
Due after one year through five years	399,388
Due after five years through ten years	808,042
Due after ten years	739,220
Amortized Cost	2,959,694	$ 2,961,430
Fair Value
Due within one year	1,021,217
Due after one year through five years	399,311
Due after five years through ten years	804,652
Due after ten years	735,977
Total	$ 2,961,157	$ 2,959,843
Weighted- Average Yield
Due within one year	2.03%
Due after one year through five years	2.02%
Due after five years through ten years	2.03%
Due after ten years	1.91%
Total	2.00%