Securities Available for Sale and Held to Maturity - Securities with Gross Unrealized Losses, Segregated by Length of Impairment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	$ 348,028	$ 349,545
Estimated Fair Value, 12 Months or More	2,677,946	2,758,879
Estimated Fair Value, Total	3,025,974	3,108,424
Gross Unrealized (Losses), Less than 12 Months	(6,870)	(3,485)
Gross Unrealized (Losses), 12 Months or More	(273,909)	(263,507)
Gross Unrealized (Losses), Total	(280,779)	(266,992)
US Treasury Securities [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	28,746	29,042
Estimated Fair Value, 12 Months or More	372,424	372,368
Estimated Fair Value, Total	401,170	401,410
Gross Unrealized (Losses), Less than 12 Months	(515)	(26)
Gross Unrealized (Losses), 12 Months or More	(23,865)	(23,811)
Gross Unrealized (Losses), Total	(24,380)	(23,837)
U.S. Government Agency Obligations [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	0	0
Estimated Fair Value, 12 Months or More	5,594	5,791
Estimated Fair Value, Total	5,594	5,791
Gross Unrealized (Losses), Less than 12 Months	0	0
Gross Unrealized (Losses), 12 Months or More	(423)	(416)
Gross Unrealized (Losses), Total	(423)	(416)
Residential Mortgage Pass-Through Securities Guaranteed by GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	14,632	9,381
Estimated Fair Value, 12 Months or More	24,950	25,967
Estimated Fair Value, Total	39,582	35,348
Gross Unrealized (Losses), Less than 12 Months	(343)	(172)
Gross Unrealized (Losses), 12 Months or More	(3,524)	(2,938)
Gross Unrealized (Losses), Total	(3,867)	(3,110)
Residential Mortgage Pass-Through Securities Issued by FNMA and FHLMC [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	303,034	309,466
Estimated Fair Value, 12 Months or More	1,259,726	1,311,865
Estimated Fair Value, Total	1,562,760	1,621,331
Gross Unrealized (Losses), Less than 12 Months	(5,957)	(3,274)
Gross Unrealized (Losses), 12 Months or More	(179,628)	(176,421)
Gross Unrealized (Losses), Total	(185,585)	(179,695)
Other Residential Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	0	0
Estimated Fair Value, 12 Months or More	214,805	230,368
Estimated Fair Value, Total	214,805	230,368
Gross Unrealized (Losses), Less than 12 Months	0	0
Gross Unrealized (Losses), 12 Months or More	(16,949)	(16,115)
Gross Unrealized (Losses), Total	(16,949)	(16,115)
Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	1,616	1,656
Estimated Fair Value, 12 Months or More	800,447	812,520
Estimated Fair Value, Total	802,063	814,176
Gross Unrealized (Losses), Less than 12 Months	(55)	(13)
Gross Unrealized (Losses), 12 Months or More	(49,520)	(43,806)
Gross Unrealized (Losses), Total	$ (49,575)	$ (43,819)