Pledged Assets (Securities Pledged as Collateral) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	$ 67,750	$ 62,168
Agency Securities Pledged As Collateral Amortized Cost	69,482	64,882
Agency Securities Pledged As Collateral Accrued Interest	296	279
Maturity Less than 30 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	56,493	58,180
Agency Securities Pledged As Collateral Amortized Cost	57,606	60,506
Agency Securities Pledged As Collateral Accrued Interest	253	266
Maturity 31 To 59 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	9,133	3,842
Agency Securities Pledged As Collateral Amortized Cost	9,581	4,227
Agency Securities Pledged As Collateral Accrued Interest	35	13
Maturity 60 To 90 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	252	146
Agency Securities Pledged As Collateral Amortized Cost	258	149
Agency Securities Pledged As Collateral Accrued Interest	1	0
Maturity over 90 days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	1,872	0
Agency Securities Pledged As Collateral Amortized Cost	2,037	0
Agency Securities Pledged As Collateral Accrued Interest	7	0
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	64,116	59,958
Credit Risk Transfer Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	595	590
Credit Risk Transfer Securities [Member] \| Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	595	590
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	3,269	1,565
US Treasury Securities [Member] \| Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	2,866	1,414
Non-Agency [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	173	206
Non-Agency [Member] \| Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	$ 173	$ 206