CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income	$ 667,000,000	$ 437,000,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	64,000,000	58,000,000
Deferred income taxes	27,000,000	(14,000,000)
Premium and discount amortization on available-for-sale securities and loss on other investments	14,000,000	43,000,000
Provisions/(benefits) for credit losses and legal and regulatory proceedings	(14,000,000)	124,000,000
Share-based compensation expense	74,000,000	74,000,000
Unrealized (gain)/loss on company-owned life insurance policies, net of expenses	(117,000,000)	76,000,000
Other	31,000,000	(4,000,000)
Net change in:
Assets segregated pursuant to regulations excluding cash and cash equivalents	(5,250,000,000)	0
Collateralized agreements, net of collateralized financings	1,000,000	(24,000,000)
Loans provided to financial advisors, net of repayments	(11,000,000)	(11,000,000)
Brokerage client receivables and other accounts receivable, net	(123,000,000)	(203,000,000)
Trading instruments, net	(90,000,000)	0
Derivative instruments, net	91,000,000	(25,000,000)
Other assets	(23,000,000)	(176,000,000)
Brokerage client payables and other accounts payable	5,471,000,000	2,937,000,000
Accrued compensation, commissions and benefits	(29,000,000)	(340,000,000)
Purchases and originations of loans held for sale, net of proceeds from sales of securitizations and loans held for sale	(67,000,000)	(9,000,000)
Net cash provided by operating activities	716,000,000	2,943,000,000
Cash flows from investing activities:
Additions to property and equipment	(62,000,000)	(71,000,000)
Increase in bank loans, net	(1,522,000,000)	(1,066,000,000)
Proceeds from sales of loans held for investment	90,000,000	25,000,000
Purchases of available-for-sale securities	(2,273,000,000)	(1,403,000,000)
Available-for-sale securities maturations, repayments and redemptions	1,067,000,000	435,000,000
Proceeds from sales of available-for-sale securities	519,000,000	0
Business acquisitions, net of cash acquired	(245,000,000)	0
Other investing activities, net	(11,000,000)	(10,000,000)
Net cash used in investing activities	(2,437,000,000)	(2,090,000,000)
Cash flows from financing activities:
Proceeds from senior notes issuances, net of debt issuance costs paid	0	495,000,000
Exercise of stock options and employee stock purchases	32,000,000	43,000,000
Increase in bank deposits	2,453,000,000	7,742,000,000
Purchases of treasury stock	(79,000,000)	(222,000,000)
Dividends on common stock	(109,000,000)	(103,000,000)
Acquisitions of and distributions to noncontrolling interests, net	0	(1,000,000)
Net cash provided by financing activities	2,269,000,000	7,951,000,000
Currency adjustment:
Effect of exchange rate changes on cash	93,000,000	(82,000,000)
Net increase in cash and cash equivalents, including those segregated pursuant to regulations	641,000,000	8,722,000,000
Cash and cash equivalents, including those segregated pursuant to regulations at beginning of year	9,634,000,000	5,971,000,000
Cash and cash equivalents, including those segregated pursuant to regulations at end of period	10,275,000,000	14,693,000,000
Cash and cash equivalents	5,851,000,000	10,648,000,000
Cash and cash equivalents segregated pursuant to regulations	4,424,000,000	4,045,000,000
Supplemental disclosures of cash flow information:
Cash paid for interest	76,000,000	92,000,000
Cash paid for income taxes, net	248,000,000	176,000,000
Cash outflows for lease liabilities	56,000,000	47,000,000
Non-cash right-of-use (“ROU”) assets recorded for new and modified leases	81,000,000	39,000,000
FHLB advances
Cash flows from financing activities:
Proceeds from Federal Home Loan Bank advances	0	850,000,000
Repayments of Federal Home Loan Bank advances and other borrowed funds	$ (28,000,000)	$ (853,000,000)