Investment Securities - Held-to-Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2024		Dec. 31, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	$ 2,307,649		$ 2,288,791
Interest Receivable	12,600		10,000
(fair value of $2,156,694 and $2,168,316, respectively)	2,306,149	[1]	2,287,291
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	35	[1]	1,760
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(149,490)	[1]	(120,735)
Debt Securities, Held-to-maturity, Fair Value	2,156,694	[1]	2,168,316
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	(1,500)	[1]	(1,500)	$ (1,500)
US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	1,251,364		1,247,310
(fair value of $2,156,694 and $2,168,316, respectively)	1,251,224		1,247,170
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	35		1,760
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(54,799)		(28,170)
Debt Securities, Held-to-maturity, Fair Value	1,196,460		1,220,760
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	(140)		(140)
Commercial Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	440,476		433,827
(fair value of $2,156,694 and $2,168,316, respectively)	440,476		433,827
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(37,840)		(30,665)
Debt Securities, Held-to-maturity, Fair Value	402,636		403,162
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	0		0
Mortgage-backed Securities, Issued by Private Enterprises
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	355,342		350,493
(fair value of $2,156,694 and $2,168,316, respectively)	355,342		350,493
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(26,226)		(29,289)
Debt Securities, Held-to-maturity, Fair Value	329,116		321,204
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	0		0
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	189,985		187,033
(fair value of $2,156,694 and $2,168,316, respectively)	189,985		187,033
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(16,702)		(11,454)
Debt Securities, Held-to-maturity, Fair Value	173,283
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	0		0
Corporate Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	70,482		70,128
Interest Receivable	13,400		13,400
(fair value of $2,156,694 and $2,168,316, respectively)	69,122		68,768
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(13,923)		(21,157)
Debt Securities, Held-to-maturity, Fair Value	55,199		47,611
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	$ (1,360)		$ (1,360)

[1] Excludes accrued interest receivable of $13.4 million at December 31, 2024 which is recorded in "Other assets" on the consolidated balance shee