Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows From Operating Activities:
Net income	$ 88,761	$ 65,512
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Depreciation and amortization	6,664	9,022
Amortization of loans and advances to financial advisors and other employees	19,141	23,611
Amortization of premium on investment portfolio	5,646	3,830
Provision for loan losses and allowance for loans and advances to financial advisors and other employees	2,658	6,259
Amortization of intangible assets	2,738	2,981
Deferred income taxes	16,487	19,873
Stock-based compensation	27,072	27,915
(Gains)/losses on sale of investments	2,884	(2,459)
Other, net	(3,871)	999
Receivables:
Brokerage clients	(56,146)	83,353
Brokers, dealers, and clearing organizations	(85,843)	469,038
Securities purchased under agreements to resell	(156,782)	(70,260)
Financial instruments owned, including those pledged	(37,363)	(131,791)
Loans originated as held for sale	(404,200)	(349,044)
Proceeds from mortgages held for sale	373,919	361,435
Loans and advances to financial advisors and other employees	(5,599)	(21,873)
Other assets	(69,119)	(87,104)
Increase/(decrease) in operating liabilities, net of liabilities assumed:
Brokerage clients	(29,277)	(96,616)
Brokers, dealers, and clearing organizations	18,703	74,655
Drafts	(30,872)	(11,022)
Financial instruments sold, but not yet purchased	180,672	55,426
Other liabilities and accrued expenses	(238,121)	(170,766)
Net cash provided by/(used in) operating activities	(371,848)	262,974
Cash Flows From Investing Activities:
Maturities and principal paydowns of available-for-sale securities	129,926	198,407
Calls and principal paydowns of held-to-maturity securities	230,172	67,473
Sale or maturity of investments	9,575	2,411
Increase in bank loans, net	(130,566)	(269,337)
Payments for:
Purchase of available-for-sale securities	(92,145)	(391,585)
Purchase of held-to-maturity securities	(379,490)	(219,500)
Purchase of investments		(150)
Purchase of fixed assets	(4,586)	(8,014)
Acquisitions, net of cash received	(29,209)	(9,070)
Net cash used in investing activities	(266,323)	(629,365)
Cash Flows From Financing Activities:
Proceeds from/(repayments of) borrowings, net	60,000	(178,000)
Proceeds from Federal Home Loan Bank advances, net	82,000	290,000
Payment of contingent consideration	(7,900)	(8,356)
Increase/(decrease) in securities sold under agreements to repurchase	112,498	(48,819)
Increase/(decrease) in bank deposits, net	(82,312)	173,478
Increase/(decrease) in securities loaned	209,590	(106,474)
Tax payments related to shares withheld for stock-based compensation plans	(36,534)	(82,954)
Proceeds from stock option exercises	774
Repurchase of common stock	(2,839)
Cash dividends on preferred stock	(2,344)	(2,344)
Cash dividends paid to common stock and equity-award holders	(8,629)
Net cash provided by financing activities	324,304	36,531
Effect of exchange rate changes on cash	3,736	2,294
Decrease in cash and cash equivalents	(310,131)	(327,566)
Cash and cash equivalents at beginning of period	787,085	986,167
Cash and cash equivalents at end of period	476,954	658,601
Supplemental disclosure of cash flow information:
(Refunds, net of taxes paid for income taxes)/cash paid for income taxes, net of refunds	(21,076)	3,573
Cash paid for interest	25,368	16,093
Noncash financing activities:
Unit grants, net of forfeitures	$ 90,678	35,273
Issuance of common stock for acquisitions		$ 9,352