Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Cash flows from operating activities:
Net income	$ 221,694	$ 225,955
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	20,161	11,799
Non-cash long-term incentive compensation expense	7,554	8,976
Depreciation and other amortization	21,440	23,244
Non-cash lease expense	17,305	29,123
(Gain) on assets held for sale	0	(650)
Retirement plan loss	20,756	0
Retirement plan funding	(1,700)	0
Other, net	(4,227)	7,795
Changes in assets and liabilities:
(Increase) decrease in securities, segregated	(272,256)	2,094
Decrease (increase) in receivables	104,484	(17,238)
(Increase) in deferred sales commissions	(28,361)	(31,697)
Increase in other liabilities of consolidated company-sponsored investment funds, net	17,182	1,595
Increase (decrease) in payables	224,090	(71,542)
(Decrease) increase in accounts payable and accrued expenses	(12,042)	50,615
Increase in accrued compensation and benefits	3,877	34,064
Cash payments to relieve operating lease liabilities	(15,892)	(7,901)
Net cash provided by operating activities	148,816	353,687
Cash flows from investing activities:
Purchases of furniture, equipment and leasehold improvements	(7,478)	(31,289)
Joint venture equalization payment	0	303,980
Net cash (used in) provided by investing activities	(7,478)	272,691
Cash flows from financing activities:
Proceeds from debt, net	30,000
Repayment of debt, net		(254,316)
Increase in overdrafts payable	0	45,688
Distributions to General Partner and Unitholders	(339,628)	(246,044)
Capital contributions (to) AB Holding	(1,109)	(891)
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(29,475)	(5,552)
Other, net	(2,730)	(3,052)
Net cash (used in) financing activities	(190,670)	(556,721)
Effect of exchange rate changes on cash and cash equivalents	12,823	(10,156)
Net (decrease) increase in cash and cash equivalents	(36,509)	59,501
Cash and cash equivalents as of beginning of the period	834,033	1,160,889	$ 1,160,889
Cash and cash equivalents as of end of the period	797,524	1,220,390	$ 834,033
Excluding Company-Sponsored Investment Funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized losses (gains) on investments	4,758	(3,734)
Equity in earnings of equity method investments	6,073	0
Changes in assets and liabilities:
(Increase) decrease in investments	(29,238)	30,595
Decrease (increase) in other assets	41,034	(52,798)
Company-Sponsored Investment Funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized losses (gains) on investments	1,744	(7,481)
Changes in assets and liabilities:
(Increase) decrease in investments	(202,080)	106,527
Decrease in other assets of consolidated company-sponsored investment funds	2,460	14,346
Cash flows from financing activities:
Terminations of non-controlling interest in consolidated company-sponsored investment funds, net	$ 152,272
Redemptions of non-controlling interest in consolidated company-sponsored investment funds, net		$ (92,554)