Investment Securities, HTM Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	$ 3,900,483	$ 3,960,451
US Treasury Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	999	999
US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,700,162	1,732,351
Residential Related Securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	956,107	961,231
Residential Related Securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	50,489	52,979
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	349,410	364,728
Commercial mortgage-related securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	782,291	778,796
Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	61,025	69,369
Not Rated [Domain]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,156	1,158
Not Rated [Domain] | US Treasury Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
Not Rated [Domain] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,156	1,158
Not Rated [Domain] | Residential Related Securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
Not Rated [Domain] | Residential Related Securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
Not Rated [Domain] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
Not Rated [Domain] | Commercial mortgage-related securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
Not Rated [Domain] | Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
AAA
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	2,969,372	3,034,630
AAA | US Treasury Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	999	999
AAA | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	769,052	806,529
AAA | Residential Related Securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	956,107	961,231
AAA | Residential Related Securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	50,489	52,979
AAA | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	349,410	364,728
AAA | Commercial mortgage-related securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	782,291	778,796
AAA | Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	61,025	69,369
AA
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	923,707	917,059
AA | US Treasury Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
AA | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	923,707	917,059
AA | Residential Related Securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
AA | Residential Related Securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
AA | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
AA | Commercial mortgage-related securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
AA | Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
A
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	6,248	7,604
A | US Treasury Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
A | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	6,248	7,604
A | Residential Related Securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
A | Residential Related Securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
A | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
A | Commercial mortgage-related securities | FNMA/FHLMC
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0	0
A | Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	$ 0	$ 0