Investment Securities - Contractual Maturities of Securities Available-for-Sale (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	$ 4,898
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	1,072,310
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	1,187,395
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	3,179,074
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	4,900
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	934,883
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	1,007,423
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(2,539,966)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	5,443,677
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	4,487,172
Agency residential MBS
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	2,536,755
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(2,000,900)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	2,536,755
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	2,000,900
Agency commercial MBS
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	200,863
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	319,981
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	17,622
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	183,664
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	270,878
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(16,352)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	538,466
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	470,894
Agency residential CMOs
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	169,206
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	322,099
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	143,836
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(274,143)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	491,305
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	417,979
Municipal securities
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	97,471
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	276,758
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	22,128
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	84,826
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	232,366
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(19,339)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	396,357
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	336,531
U.S. Treasury securities
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	4,898
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	766,332
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	4,900
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	659,302
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	0
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	771,230
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	664,202
Corporate Debt Securities
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	5,000
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	339,708
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	4,650
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	280,638
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	0
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	344,708
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	285,288
Collateralized loan obligations
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	80,330
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	28,838
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	78,358
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(27,622)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	109,168
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	105,980
Private label commercial MBS
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	1,412
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	21,969
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	1,347
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(20,306)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	23,381
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	21,653
SBA securities
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	2,644
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	12,574
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	2,441
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(11,367)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	15,218
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	13,808
Private Label Collateralized Mortgage Obligations
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	195,770
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(148,946)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	195,770
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	148,946
Asset-backed Securities
Schedule of Investments [Line Items]
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Amortized Cost, Due After Ten Years	21,319
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due Within One Year Through Five Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Five Years Through Ten Years	0
Contractual Maturities of Securities Available-for-Sale, Fair Value, Due After Ten Years	(20,991)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	21,319
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 20,991