Investments (AFS Major Security Types) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	$ 113	$ 41
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(92)	(219)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	24,259	24,001
Debt Securities, Available-for-Sale, Excluding Accrued Interest	24,280	23,823
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(1)	(3)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	201	331
Debt Securities, Available-for-Sale, Excluding Accrued Interest	200	328
US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	24	20
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	289	324
Debt Securities, Available-for-Sale, Excluding Accrued Interest	313	344
State or local housing agency obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(7)	(5)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	529	461
Debt Securities, Available-for-Sale, Excluding Accrued Interest	523	458
Other Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	159	157
Debt Securities, Available-for-Sale, Excluding Accrued Interest	161	160
Non-mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	27	25
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(8)	(8)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	1,178	1,273
Debt Securities, Available-for-Sale, Excluding Accrued Interest	1,197	1,290
Mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	86	16
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(84)	(211)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	23,081	22,728
Debt Securities, Available-for-Sale, Excluding Accrued Interest	23,083	22,533
Single Family [Member] \| U.S. obligations MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	14	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(3)	(24)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	4,534	4,421
Debt Securities, Available-for-Sale, Excluding Accrued Interest	4,545	4,398
Single Family [Member] \| Mortgage-backed securities, GSE [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(2)	(3)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	216	183
Debt Securities, Available-for-Sale, Excluding Accrued Interest	214	180
Multifamily [Member] \| Mortgage-backed securities, GSE [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	72	15
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(79)	(184)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	18,331	18,124
Debt Securities, Available-for-Sale, Excluding Accrued Interest	$ 18,324	$ 17,955

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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