Securities Securities - Amortized Cost, Allowance for Credit Losses and Estimated Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 3,570,028	$ 3,619,738
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	39,203	43,066
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	110,960	130,760
Debt Securities, Held-to-maturity, Fair Value	3,498,271	3,532,044
Securities, held-to-maturity, allowance for credit loss	(310)	(310)
Securities held to maturity, net of allowance for credit losses of $310 at both September 30, 2024 and December 31, 2023	3,569,718	3,619,428
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,211,798	1,250,431
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	7,380	76
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	39,632	54,175
Debt Securities, Held-to-maturity, Fair Value	1,179,546	1,196,332
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 at both September 30, 2024 and December 31, 2023	1,211,798	1,250,431
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	2,356,730	2,367,807
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	31,823	42,990
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	71,318	76,540
Debt Securities, Held-to-maturity, Fair Value	2,317,235	2,334,257
Securities, held-to-maturity, allowance for credit loss	(310)	(310)
Securities held to maturity, net of allowance for credit losses of $310 at both September 30, 2024 and December 31, 2023	2,356,420	2,367,497
Other Investments [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,500	1,500
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	10	45
Debt Securities, Held-to-maturity, Fair Value	1,490	1,455
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 at both September 30, 2024 and December 31, 2023	$ 1,500	$ 1,500