Operating Interest Income and Operating Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating interest income:
Loans		$ 230	$ 297	$ 395
Available-for-sale securities		244	288	279
Held-to-maturity securities		346	328	255
Margin receivables		276	264	224
Securities borrowed and other		119	102	54
Total operating interest income(1)		1,215	1,279	1,207
Operating interest expense:
Securities sold under agreements to repurchase(2)		(69)	(123)	(148)
FHLB advances and other borrowings(2)		(48)	(65)	(68)
Deposits		(4)	(8)	(13)
Customer payables and other		(8)	(9)	(9)
Total operating interest expense(3)		(129)	(205)	(238)
Net operating interest income		1,086	1,074	969
Termination of legacy wholesale funding obligations	$ 4,400	4,400
Hedging Income (Expense), Operating Interest Income		(42)	(31)	(16)
Hedging Expense (Income) Operating Interest Expense		$ (74)	$ (132)	$ (153)