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Allowance for Credit Losses (Held-to-Maturity Debt Securities by Credit Quality Indication) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Amortized Cost	$ 3,606,854	$ 3,641,055	$ 3,435,888
Less: Allowance for credit losses	(463)	(488)	(159)
Held-to-maturity securities, net of allowance for credit losses	3,606,391	3,640,567	3,435,729
U.S. government agencies
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	160,000
2021	147,804
2020	25,000
2019	4,000
Prior	2,804
Amortized Cost	339,608	339,614	264,661
U.S. government agencies \| 1-4 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	160,000
2021	147,804
2020	25,000
2019	4,000
Prior	2,804
Amortized Cost	339,608
U.S. government agencies \| 5-7 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023
2022
2021
2020
2019
Prior
Amortized Cost	0
U.S. government agencies \| 8-10 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023
2022
2021
2020
2019
Prior
Amortized Cost	0
Municipal
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	1,042
2021	6,978
2020	264
2019	618
Prior	165,818
Amortized Cost	174,720	$ 179,027	$ 180,548
Municipal \| 1-4 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	1,042
2021	6,978
2020	264
2019	618
Prior	165,818
Amortized Cost	174,720
Municipal \| 5-7 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Amortized Cost	0
Municipal \| 8-10 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Amortized Cost	0
Mortgage-backed securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	5,065
2022	606,922
2021	2,422,478
2020	0
2019	0
Prior	0
Amortized Cost	3,034,465
Mortgage-backed securities \| 1-4 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	5,065
2022	606,922
2021	2,422,478
2020	0
2019	0
Prior	0
Amortized Cost	3,034,465
Mortgage-backed securities \| 5-7 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Amortized Cost	0
Mortgage-backed securities \| 8-10 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Amortized Cost	0
Corporate notes
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	14,964
2021	0
2020	6,009
2019	7,291
Prior	29,797
Amortized Cost	58,061
Corporate notes \| 1-4 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	14,964
2021	0
2020	6,009
2019	7,291
Prior	29,797
Amortized Cost	58,061
Corporate notes \| 5-7 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Amortized Cost	0
Corporate notes \| 8-10 internal grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Amortized Cost	$ 0