CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 153	$ 40
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Provision (benefit) for loan losses	(34)	5
Depreciation and amortization (including discount amortization and accretion)	53	89
(Gains) losses on securities and other	(10)	(15)
Losses on early extinguishment of debt	0	5
Share-based compensation	8	7
Deferred tax expense	42	21
Other	4	(1)
Net effect of changes in assets and liabilities:
Increase in cash required to be segregated under federal or other regulations	(1,101)	(294)
Decrease (increase) in receivables from brokers, dealers and clearing organizations	(91)	180
Decrease (increase) in margin receivables	1,062	(545)
Increase in other assets	(5)	(18)
Increase (decrease) in payables to brokers, dealers and clearing organizations	(139)	181
Increase (decrease) in customer payables	249	(162)
Decrease in other liabilities	(95)	(23)
Net cash provided by (used in) operating activities	96	(530)
Cash flows from investing activities:
Purchases of available-for-sale securities	(1,993)	(2,002)
Proceeds from sales of available-for-sale securities	703	360
Proceeds from maturities of and principal payments on available-for-sale securities	285	404
Purchases of held-to-maturity securities	(2,378)	(699)
Proceeds from maturities of and principal payments on held-to-maturity securities	430	380
Net decrease in loans receivable	282	303
Capital expenditures for property and equipment	(20)	(16)
Proceeds from sale of real estate owned and repossessed assets	5	7
Net cash flow from derivative contracts	(38)	0
Other	20	2
Net cash used in investing activities	(2,704)	(1,261)
Cash flows from financing activities:
Net increase in deposits	2,384	1,382
Net decrease in securities sold under agreements to repurchase	(82)	(4)
Advances from FHLB	0	270
Payments on advances from FHLB	0	(270)
Net proceeds from issuance of senior notes	0	460
Payments on senior notes	0	(800)
Repurchases of common stock	(301)	0
Other	1	(5)
Net cash provided by financing activities	2,002	1,033
Decrease in cash and equivalents	(606)	(758)
Cash and equivalents, beginning of period	2,233	1,783
Cash and equivalents, end of period	1,627	1,025
Supplemental Disclosures [Abstract]
Cash paid for interest	17	108
Cash paid for income taxes, net of refunds	2	3
Non-cash investing and financing activities:
Transfers from loans to other real estate owned and repossessed assets	5	8
Conversion of convertible debentures to common stock	$ 4	$ 0