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Investment Securities - Amortized Cost to Approximate Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Available for sale securities:
Amortized Cost	$ 1,062,830	$ 1,116,954
Gross Unrealized Gains	15	50
Gross Unrealized Losses	1,557	3,317
Fair Value	1,061,288	1,113,687
Accrued interest on securities available for sale	5,100	6,700
Held to maturity securities:
Amortized Cost	1,175,167	1,204,217
Gross Unrealized Gains	2,385	973
Gross Unrealized Losses	1,374	1,655
Fair Value	1,176,178	1,203,535
Accrued interest on securities held to maturity	5,600	5,800
Treasury notes
Available for sale securities:
Amortized Cost	109,146	129,261
Gross Unrealized Gains	15	45
Gross Unrealized Losses	58	338
Fair Value	109,103	128,968
Federal agencies
Available for sale securities:
Amortized Cost	240,000	250,731
Gross Unrealized Losses	1,499	2,976
Fair Value	238,501	247,755
Mortgage-backed - Agency
Held to maturity securities:
Amortized Cost	11,976	12,016
Gross Unrealized Losses	868	822
Fair Value	11,108	11,194
Mortgage-backed - Government Agency ("Agency")
Available for sale securities:
Amortized Cost	13,044	14,465
Gross Unrealized Gains		5
Gross Unrealized Losses		3
Fair Value	13,044	14,467
Mortgage-backed - Agency - fair value option
Available for sale securities:
Amortized Cost	228,448	236,997
Fair Value	228,448	236,997
Mortgage-backed - Non-Agency multi-family
Held to maturity securities:
Amortized Cost	710,024	719,662
Gross Unrealized Losses	419	415
Fair Value	709,605	719,247
Mortgage-backed - Non-Agency residential
Available for sale securities:
Amortized Cost	472,192	485,500
Fair Value	472,192	485,500
Held to maturity securities:
Amortized Cost	453,167	472,539
Gross Unrealized Gains	2,385	973
Gross Unrealized Losses	87	418
Fair Value	$ 455,465	$ 473,094

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