Investment Securities - Analysis of the Contractual Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis Rolling Maturity[Abstract]
Due in One Year or Less	$ 1,798
Due After One Year Through Five Years	332,832
Due After Five Years Through Ten Years	598,290
Due After Ten Years	6,380
Amortized Cost, Total	939,300
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-Sale: Amortized Cost	2,752,093	$ 3,172,436
Due in One Year or Less	1,768
Due After One Year Through Five Years	309,375
Due After Five Years Through Ten Years	537,433
Due After Ten Years	4,866
Fair Value, Total	853,442
Available-for-Sale: Fair Value	2,387,324	2,844,823
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Rolling Maturities (Abstract]
Due in One Year or Less	966
Due After One Year Through Five Years	82,244
Due After Five Year Through Ten Years	60,288
Amortized Cost, Total	143,498
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Due in One Year or Less	943
Due After One Year Through Five Years	71,390
Due After Five Year Through Ten Years	48,282
Fair Value, Total	120,615
Held-to-Maturity: Amortized Cost	5,088,013
Held-to-Maturity: Fair Value	4,104,469	4,615,393
Debt Securities Issued by Government Agencies
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities: Amortized Cost	71,053
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	71,396
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	71,396
Residential - Government Agencies
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities: Amortized Cost	740,652
Available-for-Sale: Amortized Cost	740,652	828,798
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	631,947
Available-for-Sale: Fair Value	631,947	732,828
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	1,712,317
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	1,712,317
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	631,947
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	1,382,197
Held-to-Maturity: Fair Value	1,382,197	1,554,227
Residential - U.S. Government-Sponsored Enterprises
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities: Amortized Cost	841,441
Available-for-Sale: Amortized Cost	841,441	919,980
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	699,349
Available-for-Sale: Fair Value	699,349	793,871
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	2,794,307
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	2,794,307
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	699,349
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	2,275,174
Held-to-Maturity: Fair Value	2,275,174	2,571,275
Commercial - Government Agencies or Sponsored Agencies
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities: Amortized Cost	159,647
Available-for-Sale: Amortized Cost	159,647	168,242
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	131,190
Available-for-Sale: Fair Value	131,190	145,667
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	437,891
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	437,891
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	131,190
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	326,483
Held-to-Maturity: Fair Value	326,483	361,994
Mortgage-Backed Securities
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities: Amortized Cost	1,741,740
Available-for-Sale: Amortized Cost	1,741,740	1,917,020
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	1,462,486
Available-for-Sale: Fair Value	1,462,486	1,672,366
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	4,944,515
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	4,944,515
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	1,462,486
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	3,983,854
Held-to-Maturity: Fair Value	$ 3,983,854	$ 4,487,496