Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash flows from operating activities:
Net income	$ 717,550	$ 581,191	$ 462,258
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	30,434	33,358	35,300
Amortization	46,641	41,869	38,669
Equity in earnings of unconsolidated affiliates	(132,685)	(135,741)	(126,930)
Partner distributions received from unconsolidated affiliate	127,533	139,119	121,582
Stock-based compensation	53,555	58,626	31,308
Provision for losses on receivables	453	772	(238)
Deferred income tax benefit	59,237	(13,780)	(33,496)
Net (gain) loss from investments	(5,804)	(2,790)	(2,757)
Net gain from business divestiture	(94,412)	0	0
Net gain from sale of property	(1,316)	(8,151)	0
Change in other long-term liabilities	(618)	(493)	901
Change in other assets	(3,207)	(2,939)	1,273
Contract costs capitalized, net of amortization	(7,885)	(5,634)	(2,293)
Contingent consideration fair value adjustment	(5,472)	(1,547)	0
Write off of fixed assets and capitalized software	0	359	5,613
Insurance rebates received for Health and Welfare Benefit Plan Trust	14,500	0	0
Insurance rebates transferred to Health and Welfare Benefit Plan Trust	(14,500)	0	0
Other	(2,840)	(3,250)	(780)
Change in current assets and liabilities:
Receivables from investment products	(9,199)	1,768	6,128
Receivables	(147,835)	(66,391)	(43,635)
Other current assets	(5,613)	1,851	(5,714)
Advances due from unconsolidated affiliate	(2,239)	(6,896)	(760)
Accounts payable	(7,859)	2,463	(2,665)
Accrued liabilities	2,382	13,708	(37,083)
Deferred revenue	1,560	(5,129)	349
Consolidated variable interest entities related:
Net gain from investments	(7,125)	0	0
Total adjustments	(109,888)	41,152	(15,228)
Net cash provided by operating activities	607,662	622,343	447,030
Cash flows from investing activities:
Additions to property and equipment	(22,644)	(32,226)	(24,835)
Additions to capitalized software	(30,024)	(24,340)	(33,958)
Purchases of marketable securities	(157,510)	(177,025)	(143,389)
Purchases of interest in limited partnerships	(1,114)	(9,483)	0
Prepayments and maturities of marketable securities	123,800	145,345	121,095
Sales of marketable securities	0	7,572	893
Proceeds from fixed asset dispositions	3,294	9,946	0
Proceeds from business divestiture	116,020	0	0
Cash paid for acquisitions, net of cash acquired	(302,048)	(29,037)	(56,435)
Advance payment for acquisition	(118,606)	0	0
Other investing activities	(10,260)	(8,054)	(4,914)
Net cash used in investing activities	(399,092)	(117,302)	(141,543)
Cash flows from financing activities:
Payment of contingent consideration	0	0	(8,799)
Purchase and retirement of common stock	(628,135)	(500,061)	(308,854)
Proceeds from issuance of common stock	144,232	126,006	101,166
Payment of dividends	(124,198)	(120,346)	(114,837)
Non-controlling interest capital raised	18,603	0	0
Net cash used in financing activities	(589,498)	(494,401)	(331,324)
Effect of exchange rate changes on cash and cash equivalents	11,330	(5,445)	7,476
Net (decrease) increase in cash and cash equivalents and cash and cash equivalents held at consolidated variable interest entities	(369,598)	5,195	(18,361)
Interest paid	578	563	703
Non-cash investing and financing activities:
Acquisition of businesses in current assets, property and equipment, current liabilities and other long-term liabilities	0	29,000	59,972
Dividends declared but not paid	65,182	63,877	61,104
Consolidated VIEs
Consolidated variable interest entities related:
Change from investment security transactions	2,249	0	0
Net gain from investments	(7,125)	0	0
Change in other assets and liabilities	177	0	0
Cash flows from financing activities:
Cash and cash equivalents and cash and cash equivalents held at consolidated variable interest entities, beginning of year	840,193	834,998	853,359
Cash and cash equivalents and cash and cash equivalents held at consolidated variable interest entities, end of year	$ 470,595	$ 840,193	$ 834,998