Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash Flows From Operating Activities:
Net income	$ 731,379	$ 522,536	$ 662,155
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	62,398	60,533	50,615
Amortization of loans and advances to financial advisors and other employees	154,182	145,227	132,012
Amortization of premium on investment portfolio	8,732	9,871	12,156
Provision for credit losses and allowance for loans and advances to financial advisors and other employees	25,402	24,999	33,506
Amortization of intangible assets	23,568	20,929	19,595
Deferred income taxes	(30,638)	15,968	12,693
Stock-based compensation	153,762	140,263	135,505
Unrealized (gains)/losses on investments	(88)	(460)	11,892
Gain on sale of leased aircraft engines	(46,484)	(4,146)	0
Other, net	(12,238)	6,718	8,852
Receivables:
Brokerage clients, net	(55,856)	82,878	228,492
Brokers, dealers, and clearing organizations	(71,336)	5,341	156,165
Securities purchased under agreements to resell	(179,127)	(1,687)	231,704
Financial instruments owned, including those pledged	(216,060)	(131,576)	425,252
Loans originated as held for sale	(2,083,024)	(995,084)	(576,153)
Proceeds from loans held for sale	2,114,640	864,996	593,086
Loans and advances to financial advisors and other employees, net	(158,082)	(181,583)	(132,384)
Other assets	3,431	(107,859)	(66,020)
Increase/(decrease) in operating liabilities, net of liabilities assumed:
Brokerage clients	(266,048)	(35,515)	(201,588)
Brokers, dealers, and clearing organizations	(59,721)	43,060	(81,661)
Drafts	9,082	15,476	(20,405)
Financial instruments sold, but not yet purchased	114,323	12,582	(301,333)
Other liabilities and accrued expenses	268,240	(14,139)	(176,721)
Net cash provided by operating activities	490,437	499,328	1,157,415
Cash Flows From Investing Activities:
Principal paydowns, calls, maturities, and sales of available-for-sale securities	273,800	138,216	330,049
Calls and principal paydowns of held-to-maturity securities	2,190,885	101,240	114,741
Sale or maturity of investments	4,438	15,694	20,753
Sale of leased aircraft engines	69,916	0	0
Decrease/(increase) in loans held for investment, net	(1,617,763)	1,002,320	(3,822,654)
Payments for:
Purchase of available-for-sale securities	(309,329)	(19,635)	(103,339)
Purchase of held-to-maturity securities	(2,827,324)	0	(754,306)
Purchase of investments	(12,532)	(29,257)	(15,551)
Purchase of fixed assets	(73,788)	(51,976)	(82,327)
Acquisitions, net of cash received	(8,465)	(111,958)	(11,903)
Net cash provided by/(used in) investing activities	(2,310,162)	1,044,644	(4,324,537)
Cash Flows From Financing Activities:
Increase/(decrease) in securities sold under agreements to repurchase	162,526	205,633	(173,517)
Increase in bank deposits, net	1,767,648	217,468	3,836,763
Increase/(decrease) in securities loaned	43,234	67,588	(81,114)
Tax payments related to shares withheld for stock-based compensation plans	(120,962)	(94,387)	(102,546)
Repayment of senior notes	(500,000)	0	0
Repurchase of common stock	(144,097)	(443,876)	(105,831)
Cash dividends on preferred stock	(37,281)	(37,281)	(37,281)
Cash dividends paid to common stock and equity-award holders	(190,002)	(162,984)	(133,747)
Payment of contingent consideration	(962)	(6,740)	(11,313)
Net cash provided by/(used in) financing activities	980,104	(254,579)	3,191,414
Effect of exchange rate changes on cash	(6,025)	5,454	55,053
Increase/(decrease) in cash, cash equivalents, and cash segregated for regulatory purposes	(845,646)	1,294,847	79,345
Cash, cash equivalents, and cash segregated for regulatory purposes at beginning of year	3,523,849	2,229,002	2,149,657
Cash, cash equivalents, and cash segregated for regulatory purposes at end of year	2,678,203	3,523,849	2,229,002
Supplemental disclosure of cash flow information:
Cash paid for interest	995,530	821,741	220,851
Cash paid for income taxes, net of refunds	232,948	183,815	217,133
Noncash investing and financing activities:
Unit grants, net of forfeitures	$ 166,595	$ 188,641	$ 194,741