Repurchase Agreements And Other Debt (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 37,668		$ 41,754
Debt of consolidated variable interest entities, at fair value	$ 494		$ 595
Description of variable rate basis	LIBOR
Basis spread over LIBOR	39		34
Principal amount	$ 488		$ 587
Weighted average life of other debt	5 years 29 days	4 years 10 months 27 days
TBA securities Fifteen Year and Thirty Year Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Fair Value, Net	$ 46		14
TBA and Forward Settling Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Forward Settlement Value	15,540		7,430
Derivative, Fair Value, Net	46		14
US Treasury Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	45		25
Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 37,623		$ 41,729