Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash Flows From Operating Activities:
Net income	$ 371,092	$ 194,476
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Depreciation and amortization	21,680	19,235
Amortization of loans and advances to financial advisors and other employees	55,281	51,663
Amortization of premium on investment portfolio	8,907	11,119
Provision for credit losses and allowance for loans and advances to financial advisors and other employees	(14,904)	36,142
Amortization of intangible assets	8,759	9,760
Deferred income taxes	20,758	2,756
Stock-based compensation	58,571	55,223
Losses on sale of investments	553	27,758
Other, net	37,985	(8,203)
Receivables:
Brokerage clients	(395,262)	317,963
Brokers, dealers, and clearing organizations	(137,575)	44,332
Securities purchased under agreements to resell	(405,000)	(61,758)
Financial instruments owned, including those pledged	(550,985)	126,714
Loans originated as held for sale	(1,185,385)	(1,200,104)
Proceeds from mortgages held for sale	1,532,485	1,149,623
Loans and advances to financial advisors and other employees	(52,624)	(70,474)
Other assets	(140,630)	54,522
Increase/(decrease) in operating liabilities, net of liabilities assumed:
Brokerage clients	(64,290)	242,006
Brokers, dealers, and clearing organizations	93,099	66,753
Drafts	(32,849)	(29,437)
Financial instruments sold, but not yet purchased	410,932	(64,530)
Other liabilities and accrued expenses	(76,587)	(75,538)
Net cash provided by/(used in) operating activities	(435,989)	900,001
Cash Flows From Investing Activities:
Principal paydowns, calls, and maturities of available-for-sale securities	239,846	681,961
Calls and principal paydowns of held-to-maturity securities	1,002,163	155,461
Sale or maturity of investments	17,581	2,252
Disposition of business		37,000
Increase in loans held for investment, net	(1,975,039)	(875,299)
Payments for:
Purchase of fixed assets	(25,835)	(58,959)
Purchase of available-for-sale securities	(619,446)	(601,660)
Purchase of held-to-maturity securities	(1,558,941)	(384,700)
Purchase of investments	(9,055)	(12,900)
Acquisitions, net of cash received	(315)	(280)
Net cash used in investing activities	(2,929,041)	(1,057,124)
Cash Flows From Financing Activities:
Proceeds from Federal Home Loan Bank advances, net		73,000
Payment of contingent consideration	(11,313)	(21,741)
Increase/(decrease) in securities sold under agreements to repurchase	216,291	(171,746)
Increase in bank deposits, net	2,212,303	970,240
Increase/(decrease) in securities loaned	154,112	(480,133)
Tax payments related to shares withheld for stock-based compensation plans	(68,008)	(69,574)
Proceeds from preferred stock issuance, net		217,980
Proceeds from issuance of senior notes, net		394,314
Repurchase of common stock	(41,007)	(56,517)
Cash dividends on preferred stock	(16,578)	(9,687)
Cash dividends paid to common stock and equity-award holders	(31,613)	(23,131)
Cash paid to employees upon settlement of equity awards		(27,102)
Net cash provided by financing activities	2,414,187	795,903
Effect of exchange rate changes on cash	4,745	(9,978)
Increase/(decrease) in cash, cash equivalents, and cash segregated for regulatory purposes	(946,098)	628,802
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	1,506,108	1,902,772
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds	169,409	19,528
Cash paid for interest	31,634	47,650
Noncash financing activities:
Unit grants, net of forfeitures	$ 135,393	$ 113,268