CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 268	$ 293	$ 86
Adjustments to reconcile net income to net cash provided by operating activities:
Provision (benefit) for loan losses	(40)	36	143
Depreciation and amortization (including discount amortization and accretion)	325	331	395
Losses (gains) on securities and other	331	(36)	(61)
Impairment of goodwill	0	0	142
Losses on early extinguishment of debt	37	6	0
Share-based compensation	34	24	20
Deferred taxes expense (benefit)	(176)	155	107
Other	(6)	(2)	(1)
Net effect of changes in assets and liabilities:
Decrease (increase) in cash required to be segregated under federal or other regulations	(502)	511	(689)
Decrease (increase) in receivables from brokers, dealers and clearing organizations	364	(24)	(182)
Decrease (increase) in margin receivables	277	(1,322)	(549)
Increase (decrease) in payables to brokers, dealers and clearing organizations	(123)	593	227
Increase in customer payables	89	145	1,345
Proceeds from sale and collection of loans held-for-sale	0	11	15
Decrease (increase) in other assets	(22)	(132)	215
Increase (decrease) in other liabilities	(24)	112	(96)
Net cash provided by operating activities	832	701	1,117
Cash flows from investing activities:
Purchases of available-for-sale securities	(6,150)	(1,564)	(7,042)
Proceeds from sales of available-for-sale securities	3,905	1,855	3,856
Proceeds from maturities of and principal payments on available-for-sale securities	1,667	1,468	2,407
Purchases of held-to-maturity securities	(2,614)	(3,209)	(2,527)
Proceeds from maturities of and principal payments on held-to-maturity securities	1,788	1,144	1,828
Proceeds from sale of loans	40	813	0
Net decrease in loans receivable	1,337	1,273	1,724
Capital expenditures for property and equipment	(70)	(87)	(47)
Proceeds and cash transferred from sale of G1 Execution Services, LLC	0	67	0
Proceeds from sale of real estate owned and repossessed assets	28	37	62
Net cash flow from derivatives hedging assets	(2)	(15)	19
Other	73	(69)	6
Net cash provided by investing activities	2	1,713	286
Cash flows from financing activities:
Net increase (decrease) in deposits	4,555	(1,081)	(2,422)
Net increase (decrease) in securities sold under agreements to repurchase	(3,590)	(871)	88
Advances from FHLB	960	730	2,180
Payments on advances from FHLB	(1,880)	(730)	(2,180)
Net proceeds from issuance of senior notes	460	540	0
Payments on senior notes	(800)	(940)	0
Payments on trust preferred securities	(15)	0	0
Repurchases of common stock	(50)	0	0
Net cash flow from derivatives hedging liabilities	(16)	(170)	5
Other	(8)	53	2
Net cash used in financing activities	(384)	(2,469)	(2,327)
Increase (decrease) in cash and equivalents	450	(55)	(924)
Cash and equivalents, beginning of period	1,783	1,838	2,762
Cash and equivalents, end of period	2,233	1,783	1,838
Supplemental Disclosures [Abstract]
Cash paid for interest	212	318	277
Cash paid for income taxes, net of refunds	8	0	2
Non-cash investing and financing activities:
Transfers of loans held-for-investment to loans held-for-sale	39	795	41
Transfers from loans to other real estate owned and repossessed assets	27	53	75
Transfers from other real estate owned and repossessed assets to loans	0	16	0
Conversion of convertible debentures to common stock	30	5	0
Reclassification of market making business assets and liabilities to business held-for-sale	$ 0	$ 0	$ 79