Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows From Operating Activities:
Net income	$ 279,906	$ 184,859
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Depreciation and amortization	20,503	26,976
Amortization of loans and advances to financial advisors and other employees	61,783	69,393
Amortization of premium on investment portfolio	18,714	11,248
Provision for loan losses and allowance for loans and advances to financial advisors and other employees	13,980	19,025
Amortization of intangible assets	8,741	9,092
Deferred income taxes	718	14,875
Stock-based compensation	75,382	81,613
(Gains)/losses on sale of investments	10,442	(2,888)
Other, net	(86,576)	2,377
Receivables:
Brokerage clients	(82,568)	125,905
Brokers, dealers, and clearing organizations	(187,013)	689,648
Securities purchased under agreements to resell	(110,141)	(209,747)
Financial instruments owned, including those pledged	(19,048)	(139,205)
Loans originated as held for sale	(1,099,187)	(1,152,654)
Proceeds from mortgages held for sale	1,051,789	1,194,709
Loans and advances to financial advisors and other employees	(67,872)	(46,699)
Other assets	31,543	(77,373)
Increase/(decrease) in operating liabilities, net of liabilities assumed:
Brokerage clients	(200,461)	(94,594)
Brokers, dealers, and clearing organizations	180,463	63,554
Drafts	(15,404)	(17,089)
Financial instruments sold, but not yet purchased	132,511	50,291
Other liabilities and accrued expenses	(66,290)	91,896
Net cash provided by/(used in) operating activities	(48,085)	895,212
Cash Flows From Investing Activities:
Maturities and principal paydowns of available-for-sale securities	763,982	850,102
Calls and principal paydowns of held-to-maturity securities	443,295	193,140
Sale or maturity of investments	24,345	25,394
Increase in bank loans, net	(810,798)	(1,202,124)
Payments for:
Purchase of available-for-sale securities	(331,657)	(1,350,033)
Purchase of held-to-maturity securities	(1,313,587)	(712,450)
Purchase of investments	(7,578)	(1,592)
Purchase of fixed assets	(18,271)	(21,153)
Acquisitions, net of cash received	599	(6,743)
Net cash used in investing activities	(1,249,670)	(2,225,459)
Cash Flows From Financing Activities:
Repayments of borrowings, net	(257,197)	(299,000)
Proceeds from Federal Home Loan Bank advances, net	309,050	290,000
Payment of contingent consideration	(11,909)	(13,328)
Increase/(decrease) in securities sold under agreements to repurchase	261,780	(113,150)
Increase in bank deposits, net	590,000	1,356,478
Increase/(decrease) in securities loaned	471,367	(166,901)
Tax payments related to shares withheld for stock-based compensation plans	(39,815)	(76,242)
Proceeds from stock option exercises	2,278
Repurchase of common stock	(62,514)	(12,998)
Cash dividends on preferred stock	(7,031)	(7,031)
Cash dividends paid to common stock and equity-award holders	(26,023)	(6,835)
Net cash provided by financing activities	1,229,986	950,993
Effect of exchange rate changes on cash	(3,429)	7,178
Decrease in cash, cash equivalents, and cash segregated for regulatory purposes	(71,198)	(372,076)
Cash, cash equivalents, and cash segregated for regulatory purposes at beginning of period	787,085	986,167
Cash, cash equivalents, and cash segregated for regulatory purposes at end of period	715,887	614,091
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds	27,280	18,591
Cash paid for interest	111,832	49,901
Noncash financing activities:
Unit grants, net of forfeitures	119,051	55,941
Issuance of common stock for acquisitions	$ 110,671	$ 9,352