CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 379	$ 604
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	42	35
Amortization of acquired intangible assets	30	31
Non-cash lease expense	15
Deferred income taxes	36	25
Stock-based compensation	15	11
Provision for doubtful accounts on client and other receivables	4	5
Other, net	4	7
Changes in operating assets and liabilities:
Investments segregated and on deposit for regulatory purposes	(453)	503
Receivable from brokers, dealers and clearing organizations	711	(24)
Receivable from clients, net	(573)	3,172
Receivable from/payable to affiliates, net	(11)	(79)
Other receivables, net	28	18
Securities owned, at fair value	12	47
Other assets	(9)	(16)
Payable to brokers, dealers and clearing organizations	(826)	(682)
Payable to clients	284	(785)
Accounts payable and other liabilities	(161)	(110)
Net cash provided by (used in) operating activities	(473)	2,762
Cash flows from investing activities:
Purchase of property and equipment	(102)	(44)
Proceeds from sale of property and equipment	0	11
Purchase of investments available-for-sale, at fair value	0	(383)
Purchase of other investments	(4)	(11)
Proceeds from sale of other investments	0	1
Net cash used in investing activities	(106)	(426)
Cash flows from financing activities:
Proceeds from issuance of long-term debt	0	999
Payment of debt issuance costs	0	(7)
Net payments on securities sold under agreements to repurchase	0	(96)
Proceeds from senior revolving credit facilities	200	0
Principal payments on senior revolving credit facilities	(200)	0
Payment of cash dividends	(168)	(168)
Purchase of treasury stock	(143)	(114)
Purchase of treasury stock for income tax withholding on stock-based compensation	(12)	(8)
Payment for future treasury stock purchases under accelerated stock repurchase agreement	0	(12)
Net cash provided by (used in) financing activities	(323)	594
Net increase (decrease) in cash, cash equivalents, restricted cash and restricted cash equivalents	(902)	2,930
Cash, cash equivalents, restricted cash and restricted cash equivalents at beginning of period	10,193	4,548
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	9,291	7,478
Supplemental cash flow information:
Interest paid	41	31
Income taxes paid	$ 113	$ 139