Investments AFS - Unrealized Loss Position Table (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	$ 4,791,085	$ 3,213,627
AFS - Unrealized Losses - Less than 12 months	(10,474)	(7,546)
AFS - Fair Value - 12 months or longer	4,605,964	4,758,752
AFS - Unrealized Losses - 12 months or longer	(60,215)	(78,968)
AFS - Fair Value - Total in Continuous Loss Position	9,397,049	7,972,379
AFS - Unrealized Losses - Total in Continuous Loss Position	(70,689)	(86,514)
GSE obligations
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	0	3,812
AFS - Unrealized Losses - Less than 12 months	0	(38)
AFS - Fair Value - 12 months or longer	26,492	25,756
AFS - Unrealized Losses - 12 months or longer	(1,156)	(1,953)
AFS - Fair Value - Total in Continuous Loss Position	26,492	29,568
AFS - Unrealized Losses - Total in Continuous Loss Position	(1,156)	(1,991)
State or local agency obligations [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	0	15,399
AFS - Unrealized Losses - Less than 12 months	0	(432)
AFS - Fair Value - 12 months or longer	154,095	145,948
AFS - Unrealized Losses - 12 months or longer	(9,095)	(12,452)
AFS - Fair Value - Total in Continuous Loss Position	154,095	161,347
AFS - Unrealized Losses - Total in Continuous Loss Position	(9,095)	(12,884)
Non-MBS [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	937,084	894,114
AFS - Unrealized Losses - Less than 12 months	(655)	(2,099)
AFS - Fair Value - 12 months or longer	459,205	243,622
AFS - Unrealized Losses - 12 months or longer	(11,518)	(16,497)
AFS - Fair Value - Total in Continuous Loss Position	1,396,289	1,137,736
AFS - Unrealized Losses - Total in Continuous Loss Position	(12,173)	(18,596)
U.S. obligations single-family
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	281,171	146,724
AFS - Unrealized Losses - Less than 12 months	(424)	(161)
AFS - Fair Value - 12 months or longer	674,087	775,551
AFS - Unrealized Losses - 12 months or longer	(8,061)	(12,187)
AFS - Fair Value - Total in Continuous Loss Position	955,258	922,275
AFS - Unrealized Losses - Total in Continuous Loss Position	(8,485)	(12,348)
Private label MBS [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	0	0
AFS - Unrealized Losses - Less than 12 months	0	0
AFS - Fair Value - 12 months or longer	23,981	32,890
AFS - Unrealized Losses - 12 months or longer	(1,841)	(1,720)
AFS - Fair Value - Total in Continuous Loss Position	23,981	32,890
AFS - Unrealized Losses - Total in Continuous Loss Position	(1,841)	(1,720)
MBS [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	3,854,001	2,319,513
AFS - Unrealized Losses - Less than 12 months	(9,819)	(5,447)
AFS - Fair Value - 12 months or longer	4,146,759	4,515,130
AFS - Unrealized Losses - 12 months or longer	(48,697)	(62,471)
AFS - Fair Value - Total in Continuous Loss Position	8,000,760	6,834,643
AFS - Unrealized Losses - Total in Continuous Loss Position	(58,516)	(67,918)
U.S. Treasury obligations
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	937,084	874,903
AFS - Unrealized Losses - Less than 12 months	(655)	(1,629)
AFS - Fair Value - 12 months or longer	278,618	71,918
AFS - Unrealized Losses - 12 months or longer	(1,267)	(2,092)
AFS - Fair Value - Total in Continuous Loss Position	1,215,702	946,821
AFS - Unrealized Losses - Total in Continuous Loss Position	(1,922)	(3,721)
Single Family [Member] \| GSE MBS [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	2,987,199	1,283,490
AFS - Unrealized Losses - Less than 12 months	(8,886)	(2,825)
AFS - Fair Value - 12 months or longer	1,362,911	1,326,685
AFS - Unrealized Losses - 12 months or longer	(31,272)	(38,832)
AFS - Fair Value - Total in Continuous Loss Position	4,350,110	2,610,175
AFS - Unrealized Losses - Total in Continuous Loss Position	(40,158)	(41,657)
Multifamily [Member] \| GSE MBS [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
AFS - Fair Value - Less than 12 Months	585,631	889,299
AFS - Unrealized Losses - Less than 12 months	(509)	(2,461)
AFS - Fair Value - 12 months or longer	2,085,780	2,380,004
AFS - Unrealized Losses - 12 months or longer	(7,523)	(9,732)
AFS - Fair Value - Total in Continuous Loss Position	2,671,411	3,269,303
AFS - Unrealized Losses - Total in Continuous Loss Position	$ (8,032)	$ (12,193)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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