Securities Securities - Amortized Cost, Allowance for Credit Losses and Estimated Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 3,511,466	$ 3,534,085
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,668	13,954
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	217,884	187,493
Debt Securities, Held-to-maturity, Fair Value	3,297,250	3,360,546
Securities, held-to-maturity, allowance for credit loss	(310)	(310)
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2025 and December 31, 2024	3,511,156	3,533,775
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,180,113	1,193,840
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	51,161	71,076
Debt Securities, Held-to-maturity, Fair Value	1,128,952	1,122,764
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2025 and December 31, 2024	1,180,113	1,193,840
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	2,329,853	2,338,745
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,668	13,954
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	166,723	116,414
Debt Securities, Held-to-maturity, Fair Value	2,166,798	2,236,285
Securities, held-to-maturity, allowance for credit loss	(310)	(310)
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2025 and December 31, 2024	2,329,543	2,338,435
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	0	3
Debt Securities, Held-to-maturity, Fair Value	1,500	1,497
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2025 and December 31, 2024	$ 1,500	$ 1,500