Securities - Remaining Contractual Maturity of Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available-for-Sale Securities, Amortized Cost Basis [Abstract]
One year or less	$ 131,855
After one year to five years	193,902
After five years to ten years	299,113
After ten years	0
Securities that do not have a single contractual maturity date	2,226,609
Amortized Cost	2,851,479	$ 2,311,920
Available-for-Sale Securities, Fair Value [Abstract]
One year or less	133,155
After one year to five years	195,814
After five years to ten years	302,062
After ten years	0
Securities that do not have a single contractual maturity date	2,242,355
Total	2,873,386	2,272,009
Held-to-Maturity Securities, Amortized Cost [Abstract]
One year or less	8,672
After one year to five years	6,037
After five years to ten years	4,417
After ten years	2,871
Securities that do not have a single contractual maturity date	0
Amortized Cost	21,997	10,176
Held-to-Maturity Securities, Fair Value [Abstract]
One year or less	8,371
After one year to five years	5,828
After five years to ten years	4,264
After ten years	2,771
Securities that do not have a single contractual maturity date	0
Total	$ 21,234	$ 9,871