Repurchase Agreements And Reverse Repurchase Agreements (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) days	Dec. 31, 2017 USD ($)
Assets Sold under Agreements to Repurchase [Line Items]
Document Period End Date	Dec. 31, 2018
Receivable Under Reverse Repurchase Agreements	$ 21,813	$ 10,961
Securities Sold under Agreements to Repurchase	75,717	50,296
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 21,431	$ 10,467
Short-term Debt, Weighted Average Interest Rate, at Point in Time	2.79%	1.57%
Debt of consolidated variable interest entities, at fair value	$ (275)	$ (357)
Description of variable rate basis	LIBOR
Basis spread over LIBOR	40	37
Weighted average life of other debt	6 years 1 month 6 days	5 years 8 months 12 days
TBA securities Fifteen Year and Thirty Year Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Fair Value, Net	$ 70	$ 3
TBA and Forward Settling Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Forward Settlement Value	7,252	15,739
Derivative, Fair Value, Net	70	$ 3
Forward Contracts [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 10,700
Weighted Average Forward Start Days | days	9
Short-term Debt, Weighted Average Interest Rate, at Point in Time	2.90%
Bethesda Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Percentage of Repurchase Agreement Funding	35.00%	33.00%
FICC [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Percentage of Repurchase Agreement Funding	33.00%	30.00%
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 4,489	$ 2,698