Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 13,445,888	$ 9,727,401
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	518,805	710,168
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	40,065	4
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	13,924,628	10,437,565
US Treasury [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,165,702	1,084,542
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	23,333	35,091
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	9,602	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	2,179,433	1,119,633
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,059,692	1,916,581
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	31,662	71,102
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	25,089	4
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	4,066,265	1,987,679
States and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,178,135	6,683,927
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	463,810	603,975
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5,374	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	7,636,571	7,287,902
Other [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,359	42,351
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	$ 42,359	$ 42,351

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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