Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows From Operating Activities:
Net income	$ 173,015	$ 86,589
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	10,907	9,378
Amortization of loans and advances to financial advisors and other employees	26,961	27,729
Amortization of premium on investment portfolio	4,498	6,210
Provision for credit losses and allowance for loans and advances to financial advisors and other employees	(5,252)	19,253
Amortization of intangible assets	4,268	5,032
Deferred income taxes	47,253	17,098
Stock-based compensation	32,029	30,762
(Gains)/losses on sale of investments	(4,284)	31,043
Other, net	26,582	(5,464)
Receivables:
Brokerage clients	(266,101)	(117,920)
Brokers, dealers, and clearing organizations	(12,940)	(76,604)
Securities purchased under agreements to resell	(252,095)	(73,960)
Financial instruments owned, including those pledged	(287,254)	40,421
Loans originated as held for sale	(754,317)	(474,824)
Proceeds from mortgages held for sale	952,053	506,936
Loans and advances to financial advisors and other employees	(30,700)	(40,554)
Other assets	(238,950)	(51,427)
Increase/(decrease) in operating liabilities, net of liabilities assumed:
Brokerage clients	(178,278)	205,936
Brokers, dealers, and clearing organizations	44,423	106,196
Drafts	(39,591)	(29,019)
Financial instruments sold, but not yet purchased	206,784	5,943
Other liabilities and accrued expenses	20,804	(234,445)
Net cash used in operating activities	(520,185)	(5,691)
Cash Flows From Investing Activities:
Principal paydowns, calls, and maturities of available-for-sale securities	128,302	385,131
Calls and principal paydowns of held-to-maturity securities	480,635	155,184
Sale or maturity of investments	1,108	2,252
Disposition of business		37,000
Increase in loans held for investment, net	(1,079,671)	(593,296)
Payments for:
Purchase of fixed assets	(11,245)	(601,660)
Purchase of available-for-sale securities	(427,596)	(384,700)
Purchase of held-to-maturity securities	(811,473)	(53,002)
Purchase of investments	(2,675)	(12,900)
Acquisitions, net of cash received	(315)
Net cash used in investing activities	(1,722,930)	(1,065,991)
Cash Flows From Financing Activities:
Proceeds from borrowings, net		198,000
Payment of contingent consideration	(10,480)	(2,208)
Increase in securities sold under agreements to repurchase	17,273	83,894
Increase in bank deposits, net	1,318,636	1,548,352
Increase/(decrease) in securities loaned	86,577	(272,560)
Tax payments related to shares withheld for stock-based compensation plans	(66,839)	(68,497)
Repurchase of common stock	(12,038)	(56,160)
Cash dividends on preferred stock	(8,289)	(4,844)
Cash dividends paid to common stock and equity-award holders	(15,682)	(11,472)
Cash paid to employees upon settlement of equity awards		(27,101)
Net cash provided by financing activities	1,309,158	1,387,404
Effect of exchange rate changes on cash	2,336	(9,822)
(Decrease)/increase in cash, cash equivalents, and cash segregated for regulatory purposes	(931,621)	305,900
Cash, cash equivalents, and cash segregated for regulatory purposes at beginning of period	2,452,206	1,273,970
Cash, cash equivalents, and cash segregated for regulatory purposes at end of period	1,520,585	1,579,870
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds	8,394	15,423
Cash paid for interest	15,610	28,707
Noncash financing activities:
Unit grants, net of forfeitures	$ 128,639	$ 106,522