Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 0	$ 0	$ 0
Adjustments to reconcile net income to net cash provided by operating activities:
Income before allocations to partners	872	746	838
Depreciation and amortization	85	82	83
Changes in assets and liabilities:
Cash and investments segregated under federal regulations	2,581	(2,698)	(1,134)
Securities purchased under agreements to resell	(272)	(49)	(209)
Net payable to clients	(2,775)	2,846	908
Net receivable from brokers, dealers and clearing organizations	(60)	(31)	(55)
Receivable from mutual funds, insurance companies and other	(27)	(63)	(13)
Securities owned	(41)	(30)	(7)
Accrued compensation and employee benefits	223	122	14
Accounts payable, accrued expenses and other	4	(20)	19
Net cash provided by operating activities	590	905	444
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of equipment, property and improvements, net	(80)	(73)	(94)
Net cash used in investing activities	(80)	(73)	(94)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of partnership interests	80	72	352
Redemption of partnership interests	(193)	(178)	(161)
Distributions from partnership capital	(598)	(616)	(637)
Net cash used in financing activities	(711)	(722)	(446)
Net (decrease) increase in cash and cash equivalents	(201)	110	(96)
CASH AND CASH EQUIVALENTS:
Beginning of year	1,047	937	1,033
End of year	846	1,047	937
Cash paid for interest	90	75	75
Cash paid for taxes (Note 9)	10	12	12
NON-CASH ACTIVITIES:
Issuance of general partnership interests through partnership loans in current year	142	146	119
Repayment of partnership loans through distributions from partnership capital in current year	$ 111	$ 98	$ 99