Premises and Equipment Future Minimum Lease Payments Due Under non-Cancelable Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Property, Plant and Equipment [Line Items]
2021	$ 32,357
2022	30,741
2023	28,927
2024	27,487
2025	26,240
Thereafter	267,707
Total undiscounted operating lease liability	413,459
Imputed interest	$ 90,415
Weighted-average lease term in years	15 years 6 months 25 days
Weighted-average discount rate	3.10%
Other Liabilities [Member]
Property, Plant and Equipment [Line Items]
Total operating lease liability included in the accompanying balance sheet	$ 323,044	$ 323,700	$ 174,400