Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows From Operating Activities:
Net income	$ 176,048	$ 118,323
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Depreciation and amortization	13,467	16,649
Amortization of loans and advances to financial advisors and other employees	40,552	46,358
Amortization of premium on investment portfolio	11,477	5,964
Provision for loan losses and allowance for loans and advances to financial advisors and other employees	6,595	10,795
Amortization of intangible assets	5,740	6,246
Deferred income taxes	6,563	87,873
Stock-based compensation	47,642	55,266
(Gains)/losses on sale of investments	7,533	(1,855)
Other, net	(3,241)	2,111
Receivables:
Brokerage clients	(56,656)	51,312
Brokers, dealers, and clearing organizations	(213,053)	666,801
Securities purchased under agreements to resell	(53,821)	(229,503)
Financial instruments owned, including those pledged	(133,739)	(137,353)
Loans originated as held for sale	(759,874)	(749,265)
Proceeds from mortgages held for sale	779,761	821,115
Loans and advances to financial advisors and other employees	(37,174)	(33,105)
Other assets	(53,251)	(118,209)
Increase/(decrease) in operating liabilities, net of liabilities assumed:
Brokerage clients	(107,705)	(20,657)
Brokers, dealers, and clearing organizations	82,234	34,572
Drafts	(40,690)	(34,513)
Financial instruments sold, but not yet purchased	165,818	6,545
Other liabilities and accrued expenses	(99,005)	(67,666)
Net cash provided by/(used in) operating activities	(214,779)	537,804
Cash Flows From Investing Activities:
Maturities and principal paydowns of available-for-sale securities	458,662	720,828
Calls and principal paydowns of held-to-maturity securities	338,328	132,018
Sale or maturity of investments	11,942	8,642
Increase in bank loans, net	(405,094)	(571,149)
Payments for:
Purchase of available-for-sale securities	(204,907)	(986,027)
Purchase of held-to-maturity securities	(1,162,087)	(403,250)
Purchase of investments	(7,578)	(1,556)
Purchase of fixed assets	(12,299)	(16,770)
Acquisitions, net of cash received	(29,209)	(9,070)
Net cash used in investing activities	(1,012,242)	(1,126,334)
Cash Flows From Financing Activities:
Repayments of borrowings, net	(13,000)	(272,000)
Proceeds from Federal Home Loan Bank advances, net	15,000	290,000
Payment of contingent consideration	(11,909)	(11,707)
Increase/(decrease) in securities sold under agreements to repurchase	280,630	(24,547)
Increase in bank deposits, net	478,914	522,991
Increase/(decrease) in securities loaned	381,349	(124,336)
Tax payments related to shares withheld for stock-based compensation plans	(38,397)	(86,682)
Proceeds from stock option exercises	2,278
Repurchase of common stock	(45,883)	(12,998)
Cash dividends on preferred stock	(4,688)	(4,688)
Cash dividends paid to common stock and equity-award holders	(17,223)
Net cash provided by financing activities	1,027,071	276,033
Effect of exchange rate changes on cash	(2,098)	4,534
Decrease in cash, cash equivalents, and cash segregated for regulatory purposes	(202,048)	(307,963)
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	585,037	678,204
Supplemental disclosure of cash flow information:
(Refunds, net of taxes paid for income taxes)/cash paid for income taxes, net of refunds	(17,286)	17,811
Cash paid for interest	62,720	32,287
Noncash financing activities:
Unit grants, net of forfeitures	$ 104,703	48,630
Issuance of common stock for acquisitions		$ 9,352