Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 17,965,338	$ 19,908,432
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	14,828	17,158
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,401,795	1,681,985
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	16,578,371	18,243,605
US Treasury [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,212,894	5,450,546
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	285,305	398,959
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	4,927,589	5,051,587
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,463,954	7,316,824
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	9,066	8,050
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	876,338	948,638
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	6,596,682	6,376,236
States and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,245,721	7,098,635
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	5,762	9,108
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	240,152	334,388
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	5,011,331	6,773,355
Other [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,769	42,427
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	$ 42,769	$ 42,427