Investment Securities - Securities Held-to-Maturity 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, Excluding Accrued Interest, before Allowance for Credit Loss	$ 2,284,086	[1]	$ 2,270,635	[2]
Standard & Poor's, AAA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	901,579		914,499
Standard & Poor's, AA+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	1,027,500		997,563
Standard & Poor's, AA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	167,325		173,751
Standard & Poor's, A Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	1,791		1,901
Standard & Poor's, A- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		23,244
Standard & Poor's, BBB Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	44,339		20,999
Standard & Poor's, No Credit Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	43,391		43,207
Standard & Poor's, AA- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	86,149		95,471
Standard & Poor's, A+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	12,012		0
Municipal securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	1,246,249		1,243,443
Municipal securities | Standard & Poor's, AAA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	552,283		568,674
Municipal securities | Standard & Poor's, AA+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	409,001		385,990
Municipal securities | Standard & Poor's, AA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	167,325		173,751
Municipal securities | Standard & Poor's, A Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	1,791		1,901
Municipal securities | Standard & Poor's, A- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Municipal securities | Standard & Poor's, BBB Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Municipal securities | Standard & Poor's, No Credit Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	17,688		17,656
Municipal securities | Standard & Poor's, AA- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	86,149		95,471
Municipal securities | Standard & Poor's, A+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	12,012		0
Agency commercial MBS
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	432,191		427,411
Agency commercial MBS | Standard & Poor's, AAA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Agency commercial MBS | Standard & Poor's, AA+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	432,191		427,411
Agency commercial MBS | Standard & Poor's, AA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Agency commercial MBS | Standard & Poor's, A Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Agency commercial MBS | Standard & Poor's, A- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Agency commercial MBS | Standard & Poor's, BBB Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Agency commercial MBS | Standard & Poor's, No Credit Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Agency commercial MBS | Standard & Poor's, AA- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Agency commercial MBS | Standard & Poor's, A+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	349,296		345,825
Private label commercial MBS | Standard & Poor's, AAA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	349,296		345,825
Private label commercial MBS | Standard & Poor's, AA+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS | Standard & Poor's, AA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS | Standard & Poor's, A Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS | Standard & Poor's, A- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS | Standard & Poor's, BBB Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS | Standard & Poor's, No Credit Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS | Standard & Poor's, AA- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Private label commercial MBS | Standard & Poor's, A+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	186,308		184,162
U.S. Treasury securities | Standard & Poor's, AAA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities | Standard & Poor's, AA+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	186,308		184,162
U.S. Treasury securities | Standard & Poor's, AA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities | Standard & Poor's, A Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities | Standard & Poor's, A- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities | Standard & Poor's, BBB Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities | Standard & Poor's, No Credit Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities | Standard & Poor's, AA- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
U.S. Treasury securities | Standard & Poor's, A+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Corporate Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	70,042		69,794
Corporate Debt Securities | Standard & Poor's, AAA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Corporate Debt Securities | Standard & Poor's, AA+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Corporate Debt Securities | Standard & Poor's, AA Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Corporate Debt Securities | Standard & Poor's, A Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Corporate Debt Securities | Standard & Poor's, A- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		23,244
Corporate Debt Securities | Standard & Poor's, BBB Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	44,339		20,999
Corporate Debt Securities | Standard & Poor's, No Credit Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	25,703		25,551
Corporate Debt Securities | Standard & Poor's, AA- Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0		0
Corporate Debt Securities | Standard & Poor's, A+ Rating
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	$ 0		$ 0

[1] Excludes accrued interest receivable of $11.3 million at September 30, 2023 which is recorded in "Other assets" on the condensed consolidated balance sheets

[2] Excludes accrued interest receivable of $13.5 million at December 31, 2022 which is recorded in "Other assets" on the condensed consolidated balance sheets