Investment Securities - Securities Held-to-Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2023		Mar. 31, 2023	Dec. 31, 2022		Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	$ 2,279,702	[1]		$ 2,270,635	[2]
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	(1,500)	[1]	$ (1,500)	(1,500)	[2]	$ (1,500)	$ 0	$ 0
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Total	2,278,202	[1]		2,269,135	[2]
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	173	[1]		8	[2]
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(157,563)	[1]		(158,671)	[2]
Debt Securities, Held-to-maturity, Fair Value	2,120,812	[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	1,245,462			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	1,245,322			1,243,303
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	173			8
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(53,811)			(77,526)
Debt Securities, Held-to-maturity, Fair Value	1,191,684			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	430,578			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	430,578			427,411
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0			0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(35,178)			(34,287)
Debt Securities, Held-to-maturity, Fair Value	395,400			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	348,123			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	348,123			345,825
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0			0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(34,612)			(26,027)
Debt Securities, Held-to-maturity, Fair Value	313,511			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	185,581			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	185,581			184,162
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0			0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(12,987)			(12,462)
Debt Securities, Held-to-maturity, Fair Value	172,594			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	69,958			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	68,598			68,434
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0			0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(20,975)			(8,369)
Debt Securities, Held-to-maturity, Fair Value	47,623			60,065
Interest Receivable	$ 13,400			$ 13,500

[1] Excludes accrued interest receivable of $13.4 million at June 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