Investments (AFS Major Security Types) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	$ 238	$ 211
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(24)	(28)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	27,204	27,336
Debt Securities, Available-for-Sale, Excluding Accrued Interest	27,418	27,519
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	0	0
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	6	14
Debt Securities, Available-for-Sale, Excluding Accrued Interest	6	14
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	28	30
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	279	280
Debt Securities, Available-for-Sale, Excluding Accrued Interest	307	310
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	3	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(1)	(1)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	413	369
Debt Securities, Available-for-Sale, Excluding Accrued Interest	415	370
Other Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
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	18	18
Debt Securities, Available-for-Sale, Excluding Accrued Interest	19	19
Non-mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	32	33
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(1)	(1)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	716	681
Debt Securities, Available-for-Sale, Excluding Accrued Interest	747	713
Mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	206	178
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(23)	(27)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	26,488	26,655
Debt Securities, Available-for-Sale, Excluding Accrued Interest	26,671	26,806
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	45	25
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	(1)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	5,840	5,683
Debt Securities, Available-for-Sale, Excluding Accrued Interest	5,885	5,707
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	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(1)	(1)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	208	217
Debt Securities, Available-for-Sale, Excluding Accrued Interest	208	217
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	160	152
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(22)	(25)
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss	20,440	20,755
Debt Securities, Available-for-Sale, Excluding Accrued Interest	$ 20,578	$ 20,882

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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