Investment Securities - Securities Held-to-Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 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	$ 2,275,150	[1]	$ 2,270,635	[2]
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	(1,500)	[1]	(1,500)	[2]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Total	2,273,650	[1]	2,269,135	[2]
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	814	[1]	8	[2]
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(117,408)	[1]	(158,671)	[2]
Debt Securities, Held-to-maturity, Fair Value	2,157,056	[1]	2,110,472	[2]
Municipal securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	1,244,441		1,243,443
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	(140)		(140)
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Total	1,244,301		1,243,303
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	814		8
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(41,203)		(77,526)
Debt Securities, Held-to-maturity, Fair Value	1,203,912		1,165,785
Agency commercial MBS
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	428,995		427,411
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	0		0
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Total	428,995		427,411
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(26,135)		(34,287)
Debt Securities, Held-to-maturity, Fair Value	402,860		393,124
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	346,976		345,825
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	0		0
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Total	346,976		345,825
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(28,371)		(26,027)
Debt Securities, Held-to-maturity, Fair Value	318,605		319,798
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	184,862		184,162
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	0		0
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Total	184,862		184,162
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(8,233)		(12,462)
Debt Securities, Held-to-maturity, Fair Value	176,629		171,700
Corporate Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	69,876		69,794
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	(1,360)		(1,360)
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Total	68,516		68,434
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0		0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(13,466)		(8,369)
Debt Securities, Held-to-maturity, Fair Value	55,050		60,065
Interest Receivable	$ 11,300		$ 13,500

[1] Excludes accrued interest receivable of $11.3 million at March 31, 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